Caterpillarengine - trucktransmission-onhighway
Caterpillar CX28
Maintenance schedule, common problems & OEM parts breakdown
The Cat CX28 is not an engine in its own right — it is Caterpillar's smallest on-highway automatic transmission, a six-speed electronically controlled planetary unit built in an aluminum case for weight savings over off-road transmissions. It pairs with the Cat C7 (7.2 L) or C9 (8.8 L) diesel, rated up to 298 kW (400 hp) and 1695 N·m (1250 lb-ft) of torque in commercial service, and up to 336 kW (450 hp) in its militarized C9 pairing. Caterpillar launched the CX line, including the CX28, CX31, and CX35, around 2005-2006 for medium- and heavy-duty vocational trucks, motorcoach and RV chassis, and later a BAE Systems Caiman MRAP military chassis. The unit carries three PTO locations (two on the converter housing, one high-output pad at the rear) and mounts on a three-point base. A standalone CX28 weight figure is not published; sibling CX31/CX35 units in the same family run roughly 420 to 510 kg (925 to 1125 lb) with rear PTO, so the CX28 sits below that range.
Caterpillar built the CX family to compete with Allison in medium-duty automatics, with the CX28 as the entry unit below the higher-horsepower CX31 and CX35, and a larger CX48 later added for oilfield work. When Caterpillar exited the US on-highway diesel engine business in 2010 rather than adopt urea-SCR aftertreatment, and then dropped its on-highway vocational truck line by 2016, the C7/C9 on-highway engine pairing the CX28 depended on stopped production, and no direct on-highway successor followed. Unlike the CX31 and CX35, which live on today as CX31-P600 and CX35-P800 well-service transmissions, Caterpillar never built a CX28 oilfield variant. In today's used and parts market, surviving CX28 units are mostly pulls from demilitarized or salvaged Caiman MRAP chassis and from the shrinking pool of pre-2010 Cat-powered motorcoaches and vocational trucks, making it a legacy component supported mainly through dealer parts lookup and shared CX-series service literature rather than active factory development.
Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.
Caterpillar CX28 specifications
Engine
| Identity | CX28 is Cat's on-highway automatic transmission, not an engine or a standalone truck model. It has no cylinders or displacement of its own; it bolts to a diesel engine's flywheel housing. |
| Engine pairing | Built and marketed as an integrated package with the Cat C7 and C9 diesel engines only, for medium-duty vocational trucks, RV/motorcoach chassis, and some armored-truck chassis. No non-Cat engine pairing is documented. |
| Rated input power/torque | Rated to handle engine output of roughly 261-317 kW (350-425 hp); Cat's own product-launch figures round this to "up to 298 kW (400 hp)". Input torque capacity is cited as 1,700-1,830 N·m in parts cross-reference data, or "up to 1,695 N·m (1,250 lb-ft)" in Cat's press material — figures vary slightly by source and by which ratio/case build is fitted. |
| Rated input speed | Up to 2,400 rpm at the torque converter input. |
| Control system | Electronically managed by a dedicated powertrain electronic control module, with transmission-oil-temperature and output-speed sensors governing shift quality and torque-converter lock-up timing. |
Weights
| Base transmission weight | Approximately 270 kg (595 lb) dry for the CX28 case, per parts cross-reference data. It carries the smallest (28 cm) clutch pack in the CX family, so it sits lighter than the CX31 (925 lb / 420 kg with rear PTO) and CX35 (1,125 lb / 510 kg with rear PTO) siblings — confirm exact mass for a specific ratio/PTO configuration against dealer service literature. |
| Weight vs off-road planetary transmissions | The CX family's aluminum case is reported to cut weight by up to roughly 410 kg (900 lb) versus comparable off-road/iron-case planetary transmissions — published for the CX line generally, not confirmed as a CX28-specific figure. |
| Ground pressure | Not applicable — this is a driveline component, not a machine with ground contact. |
Dimensions
| Clutch pack diameter | 28 cm multi-disc clutch — the dimension the model designation is built around. |
| Case length | 838 mm (33.0 in) for one case build, 856 mm (33.7 in) for a longer case build with a different rear output/PTO arrangement — length varies by configuration. |
| Overall width/height | Not published in available technical literature. The case is sized to bolt directly to the C7/C9 flywheel housing (SAE-pattern bellhousing); installation and cooling-system guides define mounting and clearance, not full overall dimensions. |
Performance
| Gear count | Six forward speeds and one reverse, full-range planetary automatic with electronic shift control and torque-converter lock-up. |
| Gear ratios | One documented ratio set tied to this model: 1st 3.76, 2nd 1.96, 3rd 1.37, 4th 1.00 (direct), 5th 0.77, 6th 0.65 (overdrive), reverse 3.97 — overall ratio spread about 5.78:1. A second, differently-sourced ratio set has also been cited for this model in some configuration listings (1st 5.08, 2nd 3.35, 3rd 2.58, 4th 1.79, 5th 1.39, 6th 1.00, reverse 5.39); this set is not independently confirmed and should be treated as an alternate/unverified build until checked against the transmission's own nameplate or OEM literature. |
| Input rating | Handles roughly 261-317 kW (350-425 hp) and 1,700-1,830 N·m (1,254-1,350 lb-ft) of engine input, consistent with Cat's rounded "up to 400 hp / 1,250 lb-ft" launch figures. |
| PTO provision | Rear-mount high-output PTO location plus side-mount PTO positions at the 10 o'clock or 2 o'clock locations on the torque converter housing. Third-party side-mount PTO units for this transmission are rated in roughly the 47-82 kW (63.6-109.4 hp) range depending on the unit selected. |
| Travel speed / drawbar / gradeability | Not applicable — the CX28 is a driveline component, not a complete vehicle. Actual road speed, grade performance, and drawbar/tractive effort depend on the installed truck's axle ratio, tire size, and GVW, not on the transmission alone. |
Service capacities (summary)
| Transmission fluid type | Cat TDTO (TO-4/TO-4M) transmission and drive train oil, or an approved equivalent meeting TO-4 specification. |
| Transmission fluid capacity | Not consistently documented for this exact build across available sources. Confirm the approved fill volume against the transmission's own service/installation literature before servicing — do not assume a shared figure with the CX31/CX35 siblings. |
| Cooling system | Uses a dedicated on-highway transmission cooling circuit per the applicable cooling-system installation guide; capacity not published. |
| Fuel tank / engine oil / engine cooling | Not applicable to this component — those capacities belong to the host truck and its C7/C9 engine, not to the transmission itself. |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
CX28 fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Transmission oil (CX28 planetary automatic — torque converter, clutch packs, and gear train share one common sump) | No CX28-specific refill figure is confirmed in available Caterpillar literature. The next-size sibling in the same on-highway family, CX31, documents 38-49 L (10-13 US gal) initial fill and 20-27 L (5.3-7 US gal) service refill across its shallow-sump, standard-sump, and retarder-equipped builds. CX28 is the lighter-duty member of that family (paired with Cat C7/C9, rated to 400 hp / 1250 lb-ft versus CX31's 500 hp / 1650 lb-ft), so its own sump runs at or below the CX31 shallow-sump figure — treat that only as a directional range, not a confirmed CX28 number. Total system volume (sump plus external cooler and lines) also varies with the cooler routing chosen by the truck, motorhome, or bus chassis builder. Set final fill level by the sight gauge/dipstick reading called for in the CX28 Operation and Maintenance Manual rather than a fixed poured quantity. | Cat AT-1 automatic transmission fluid, developed specifically for the CX-series on-highway transmission line (CX28/CX31/CX35). Cat's newer full-synthetic ATF HD is also tested and approved for this same transmission family. No cold-climate viscosity split is published for this fluid the way engine oil charts split by ambient temperature; use the single fluid grade as specified. Do not substitute automotive Dexron ATF or Cat TDTO power-shift oil (used in Cat's off-highway construction-equipment transmissions) unless the specific chassis OMM explicitly calls for it. Check level electronically or by dipstick with the transmission in neutral, engine at idle, and sump oil above 80 C (176 F). |
| Transmission oil filter | Filter element only — no separate fluid volume beyond the sump fill already covered above. | Change at the interval the CX28 Operation and Maintenance Manual sets for the transmission section (by hours, months, or duty cycle, whichever comes first). Use the transmission-specific spin-on/cartridge element; fluid fill after a filter change is the same AT-1/ATF HD fluid noted above. Caterpillar also recommends periodic oil sampling on this transmission to confirm the fluid hasn't picked up contamination between scheduled changes. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar CX28 maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the CX28 beyond the schedule
Predictive Maintenance & Fluid Analysis
Run scheduled oil sampling on every fluid change to catch clutch-pack and gearset wear metal before it shows up as a shift complaint. The CX28 runs Cat ATF-HD or an AT-1/Dexron IIIH-spec fluid; watch for darkening or a burnt odor between intervals as an early sign of clutch slip. The magnetic screen is your cheapest wear-trend indicator — check it every service, not just when there's a complaint. On militarized Caiman chassis, correlate transmission fault codes with C9 engine data since both share cooling and electrical harness routing.
Corrective & Common Repairs
Most CX28 comebacks trace to PTO seal weeping, torque-converter lock-up clutch shudder, or shift-selector electrical faults from corroded harness connectors — the last one especially common on water-fording MRAP chassis. Chafed cooler lines and clogged breathers cause slow overheating that gets misdiagnosed as a clutch problem. Valve body solenoids are a common wear item once shift quality gets harsh or delayed. Confirm electrical faults with a dealer scan tool before pulling the unit, since many shift complaints are connector corrosion, not internal wear.
Overhaul & Rebuild Points
A rebuild centers on the clutch packs, planetary gearsets, and the torque converter's one-way stator clutch — inspect all three for wear beyond limits before returning the unit to service. Reseal the case, cooler lines, and converter housing as a set rather than piecemeal. Check the aluminum case around the mount bosses and rear PTO pad for cracking on units that saw sustained PTO duty or MRAP chassis shock loading. Always recalibrate the ECM and reconfirm shift-selector operation after reassembly before road test.
Seasonal & Environment Servicing
Dusty and sandy service (common on former MRAP chassis) clogs the case breather and packs grit into the cooler fins — clean both more often than the standard interval. Water-fording history means checking harness connectors and seals for intrusion before trusting the electronics. Cold-climate motorcoach and RV use needs the correct fluid viscosity grade for clean cold shifts, while sustained high-idle or PTO generator duty in hot climates calls for closer cooler-flow checks to keep clutch-pack temperatures in range.
CX28 common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 126-1817 | Filter-Oil | Hydraulic service | Check fitment → |
| 249-2329 | Filter Element As-Oil | Hydraulic service | Check fitment → |
| 280-7427 | Filter Element As-Oil | Hydraulic service | Check fitment → |
| 280-7424 | Filter Element As-Oil | Hydraulic service | Check fitment → |
| 126-1815 | Filter-Oil | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
CX28 fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Amber (diagnostic) shift-selector lamp | Transmission electronic control has logged a diagnostic trouble code; general check-transmission alert | Sensor, wiring, or shift-selector communication fault detected by the transmission control unit | Read active and inactive codes at the shift selector or with Cat ET before clearing; note the code and the conditions present when it set |
| Red warning lamp (transmission) | Transmission oil temperature has exceeded the safe limit, or the oil filter has gone into bypass | Sustained high-load or steep-grade operation, undersized or restricted oil cooler, low fluid level, or a plugged filter | Stop and idle in Neutral to cool the unit, check fluid level and cooler airflow, inspect or replace the filter if bypass is confirmed |
| OL - OK (oil level check mode) | Shown on the shift selector when the electronic oil-level check confirms fluid is within the correct band | Normal confirmation reading, not a fault | No action needed; recheck with the dipstick if the two readings disagree, since the sensor compensates for fluid temperature |
| OL - (invalid or delayed reading) | Oil level check could not complete because setup conditions were not met | Level check attempted while driving, engine not at idle, transmission not in Neutral, or fluid outside the required temperature window | Park on level ground, set the parking brake, shift to Neutral, let the engine idle and fluid settle for roughly two minutes, then repeat the check |
| Transmission overheat protection / limp condition | Control system limits operation to protect the unit after prolonged high oil temperature | Parking brake left applied with the transmission in gear, first-gear lock-up or rear-axle gearing not matched to the application, or an undersized oil cooler | Enable auto-neutral-at-park-brake if equipped, confirm gearing matches the duty cycle and grade, verify cooler sizing and airflow with the dealer |
| Lost communication with shift selector | Transmission control unit cannot communicate with the shift-selector module over the data link, which can leave the truck unable to shift out of Park or Neutral, or unable to start | Corroded, loose, or damaged connector pins along the selector-to-control-unit harness, often surfacing after harness work or in wet or salted environments | Inspect, clean, and reseat harness connectors and grounds along the selector run before condemning the control module |
| Retarder/output communication fault (reduced road speed limp mode) | Data-link style fault between the transmission control and an auxiliary retarder controller that forces a speed-limited limp mode | Wiring or connector fault, or corrosion, between the transmission control unit and the retarder controller | Check wiring and connectors between the transmission control and retarder controller, verify power and ground circuits, clear the code after repair and confirm it does not return |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
All CX28 assemblies by section
Every catalogued assembly group for the Caterpillar CX28. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Basic Transmission
293-3622 Carrier Gp-Planetary
| 25***94 | Bearing-Thrust | 1 |
| 25***45 | Bearing As-Roller | 12 |
| 25***52 | Pin-Spring | 6 |
256-6354 Carrier Gp-Planetary
| 25***45 | Gear-Ring; (88-Teeth) | 1 |
| 25***53 | Gear-Planetary; (23-Teeth) | 4 |
| 25***54 | Carrier Group-Planetary | 1 |
293-9143 Clutch Gp-Transmission
| 09***94 | Pin, Dowel | 1 |
| 25***43 | Drum As | 1 |
| 25***49 | Bushing | 1 |
293-9087 Clutch Gp-Transmission
| 09***94 | Pin, Dowel | 1 |
| 25***43 | Drum As | 1 |
| 25***49 | Bushing | 1 |
293-9088 Clutch Gp-Transmission
| 25***57 | Plate-Backing | 1 |
| 25***87 | Plate-Backing | 1 |
| 25***22 | Piston | 2 |
310-1106 Housing Gp-Planetary
| 25***58 | Bearing-Needle | 1 |
| 27***47 | Sleeve | 1 |
| 27***13 | Ring-Seal | 3 |
310-1105 Housing Gp-Planetary
| 25***58 | Bearing-Needle | 1 |
| 27***47 | Sleeve | 1 |
| 27***13 | Ring-Seal | 3 |
310-1104 Housing Gp-Planetary
| 25***54 | Sleeve | 1 |
| 25***58 | Bearing-Needle | 1 |
| 27***47 | Sleeve | 1 |
296-7529 Housing Gp-Planetary
| 25***53 | Plate-Wear | 1 |
| 25***57 | Plate-Support | 1 |
| 25***58 | Bearing-Needle | 1 |
311-7626 Planetary Gp-Transmission
| 03***13 | Seal-O-Ring | 3 |
| 21***68 | Seal-O-Ring; (11.89-mm Id) | 6 |
| 25***54 | Carrier Group-Planetary | 1 |
293-9144 Planetary Gp-Transmission
| 00***16 | Ring | 2 |
| 03***13 | Seal-O-Ring | 3 |
| 1T***43 | Ball Bearing | 1 |
293-9093 Planetary Gp-Transmission
| 03***13 | Seal-O-Ring | 3 |
| 25***54 | Carrier Group-Planetary | 1 |
| 25***83 | Support Group-Transmission; -Charge Pump | 1 |
311-7627 Planetary Gp-Transmission
| 03***13 | Seal-O-Ring | 3 |
| 21***68 | Seal-O-Ring; (11.89-mm Id) | 6 |
| 25***54 | Carrier Group-Planetary | 1 |
311-7628 Planetary Gp-Transmission
| 00***16 | Ring | 2 |
| 03***13 | Seal-O-Ring | 3 |
| 1T***43 | Ball Bearing | 1 |
256-6335 Planetary Gp-Transmission
| 21***25 | Bearing As-Roller | 8 |
| 25***35 | Planetary Group-Transmission | 1 |
| 25***36 | Gear-Planetary; (29 Teeth) | 4 |
295-8477 Planetary Gp-Transmission -Front
| 03***13 | Seal-O-Ring | 3 |
| 25***54 | Carrier Group-Planetary | 1 |
| 25***88 | Disc-Friction | 6 |
311-1530 Power Train Ar -6-Speed
| 23***09 | Plug As-Connector; (12-Pin) | 1 |
| 25***62 | Control Group-Transmission; -Keypad Shifter | 1 |
| 29***60 | Control Group-Transmission; -Keypad Shifter | 1 |
317-9068 Transmission Ar -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***36 | Control Group-Transmission Hydraulic | 1 |
311-7637 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
293-9104 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
293-9099 Transmission Ar -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
311-7638 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***16 | Torque Converter Group | 1 |
311-7633 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
293-9102 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***15 | Torque Converter Group | 1 |
311-4897 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***16 | Torque Converter Group | 1 |
311-7641 Transmission Ar -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
311-7635 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***15 | Torque Converter Group | 1 |
293-9105 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***16 | Torque Converter Group | 1 |
293-9098 Transmission Ar -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
311-7636 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***71 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
293-9103 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***71 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
314-6893 Transmission Ar -6-Speed
| 26***72 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
| 28***04 | Control Group-Transmission Hydraulic | 1 |
311-7644 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***16 | Torque Converter Group | 1 |
293-9101 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***72 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
311-7634 Transmission Ar -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***72 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
293-9100 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
311-4896 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
311-7645 Transmission Ar -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
311-7642 Transmission Ar -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
313-4913 Transmission Ar-Complete -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***71 | Torque Converter Group | 1 |
| 27***30 | Cover Group-Access; -Fuel Priming Pump | 1 |
299-8030 Transmission Ar-Complete -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***36 | Control Group-Transmission Hydraulic | 1 |
314-6892 Transmission Ar-Complete -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***36 | Control Group-Transmission Hydraulic | 1 |
287-5738 Transmission Ar-Complete -6-Speed
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
321-6409 Transmission Ar-Complete
| 26***56 | Plate Group-Drive | 1 |
| 26***65 | Torque Converter Group | 1 |
| 28***04 | Control Group-Transmission Hydraulic | 1 |
315-5060 Transmission Ar-Complete -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 26***72 | Torque Converter Group | 1 |
| 27***30 | Cover Group-Access; -Fuel Priming Pump | 1 |
321-0054 Transmission Ar-Complete
| 26***54 | Plate Group-Drive | 1 |
| 27***34 | Yoke Group | 1 |
| 27***16 | Torque Converter Group | 1 |
330-4124 Transmission Ar-Complete -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***15 | Torque Converter Group | 1 |
| 28***95 | Yoke Group | 1 |
313-7708 Transmission Ar-Complete -6-Speed
| 26***72 | Torque Converter Group | 1 |
| 27***34 | Yoke Group | 1 |
| 28***04 | Control Group-Transmission Hydraulic | 1 |
321-3502 Transmission Ar-Complete -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***15 | Torque Converter Group | 1 |
| 28***04 | Control Group-Transmission Hydraulic | 1 |
320-0922 Transmission Ar-Complete -6-Speed
| 26***54 | Plate Group-Drive | 1 |
| 27***15 | Torque Converter Group | 1 |
| 27***96 | Filter Group-Oil | 1 |
310-7363 Transmission Ar-Complete -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***36 | Control Group-Transmission Hydraulic | 1 |
319-8144 Transmission Ar-Complete -6-Speed
| 26***30 | Bracket-Mounting | 2 |
| 29***60 | Control Group-Transmission; -Keypad Shifter | 1 |
| 29***72 | Core Group-Oil Cooler; -Transmission | 1 |
317-2113 Transmission Ar-Complete -6-Speed
| 25***73 | Torque Converter Group | 1 |
| 26***56 | Plate Group-Drive | 1 |
| 27***36 | Control Group-Transmission Hydraulic | 1 |
311-4894 Transmission Ar-Core
| 29***44 | Planetary Group-Transmission | 1 |
| 30***89 | Housing Group-Torque Converter | 1 |
| 31***94 | Transmission Ar-Core | 1 |
295-8481 Transmission Ar-Core
| 29***77 | Planetary Group-Transmission; -Front | 1 |
| 29***78 | Housing Group-Torque Converter | 1 |
| 29***81 | Transmission Ar-Core | 1 |
311-7629 Transmission Ar-Core
| 29***78 | Housing Group-Torque Converter | 1 |
| 31***26 | Planetary Group-Transmission | 1 |
| 31***29 | Transmission Ar-Core | 1 |
311-7630 Transmission Ar-Core
| 25***44 | Housing Group-Torque Converter | 1 |
| 31***27 | Planetary Group-Transmission | 1 |
| 31***30 | Transmission Ar-Core | 1 |
311-7631 Transmission Ar-Core
| 30***89 | Housing Group-Torque Converter | 1 |
| 31***28 | Planetary Group-Transmission | 1 |
| 31***31 | Transmission Ar-Core | 1 |
293-9097 Transmission Ar-Core
| 25***44 | Housing Group-Torque Converter | 1 |
| 29***93 | Planetary Group-Transmission | 1 |
| 29***97 | Transmission Ar-Core | 1 |
Cooling System
299-5772 Core Gp-Oil Cooler -Transmission
| 0S***18 | Bolt; (5/16-18x1-In)(Hydraulic Pump) | 8 |
| 21***97 | Seal-O-Ring | 2 |
| 29***09 | Bonnet | 2 |
299-5408 Core Gp-Oil Cooler -Transmission
| 0S***18 | Bolt; (5/16-18x1-In)(Hydraulic Pump) | 8 |
| 21***97 | Seal-O-Ring | 2 |
| 29***08 | Core Group-Oil Cooler; -Transmission | 1 |
Electrical System
7x-6312 Cord As-Heater Element -120-Volt
| 7X***12 | Cord As-Heater Element; -120-Volt | 1 |
127-8609 Cord As-Heater Element -240-Volt
| 12***09 | Cord As-Heater Element; -240-Volt | 1 |
312-6109 Electronics Gp-Power Train
| 31***09 | Electronics Group-Power Train | 1 |
| 33***09 | Software Group-Power Train | 1 |
| 33***10 | Service Group-Power Train | 1 |
290-3348 Electronics Gp-Power Train
| 29***56 | Software Group-Power Train | 1 |
| 29***57 | Service Group-Power Train | 1 |
| 29***48 | Electronics Group-Power Train | 1 |
312-6108 Electronics Gp-Power Train
| 31***08 | Electronics Group-Power Train | 1 |
| 32***97 | Software Group-Power Train | 1 |
| 32***98 | Service Group-Power Train | 1 |
332-4745 Heater As-Fluid
| 13***17 | Cap As-Dust | 1 |
| 33***45 | Heater As-Fluid | 1 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 1 |
330-6557 Heater As-Fluid
| 13***17 | Cap As-Dust | 1 |
| 33***57 | Heater As-Fluid | 1 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 1 |
332-6775 Heater Gp-Fluid
| 33***57 | Heater As-Fluid | 1 |
| 33***75 | Heater Group-Fluid | 1 |
| 7X***12 | Cord As-Heater Element; -120-Volt | 1 |
332-6776 Heater Gp-Fluid
| 12***09 | Cord As-Heater Element; -240-Volt | 1 |
| 33***45 | Heater As-Fluid | 1 |
| 33***76 | Heater Group-Fluid | 1 |
234-5013 Sensor Gp-Temperature
| 23***13 | Sensor Group-Temperature; -Air Inlet Manifold | 1 |
| 25***53 | Sensor As-Temperature; (Torque Converter Outlet Oil) | 1 |
| 8L***86 | Seal-O-Ring (Id=16.36mm); (16.36-mm Id) | 1 |
325-0612 Switch Gp-Pressure -Differential
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 2 |
Operator Station
227-4283 Bracket Gp-Mounting -Messenger Display
| 20***75 | Bracket | 2 |
| 22***83 | Bracket Group-Mounting; -Messenger Display | 1 |
| 5H***55 | Lockwasher; (To Switch As) | 2 |
298-3860 Control Gp-Transmission -Keypad Shifter
| 26***30 | Bracket-Mounting | 2 |
| 29***60 | Control Group-Transmission; -Keypad Shifter | 1 |
320-2982 Control Gp-Transmission -Rh
| 13***00 | Clip; (Tab) | 2 |
| 24***94 | Receptacle As-Connector; (12-Pin) | 1 |
| 26***24 | Plug As-Connector; (4-Pin) | 1 |
255-6262 Control Gp-Transmission -Keypad Shifter
| 25***62 | Control Group-Transmission; -Keypad Shifter | 1 |
302-0416 Display Gp-Monitor -Messenger
| 24***43 | Control Group-Unprgmed Monitor; (Messenger) | 1 |
| 30***16 | Display Group-Monitor; -Messenger | 1 |
Transmission Case &Amp; Mounting
257-8677 Case Gp-Transmission
| 25***77 | Case Group-Transmission | 1 |
| 26***91 | Insert-Threaded; (M16x2-Thd) | 6 |
| 28***02 | Plug | 3 |
327-5260 Case Gp-Transmission
| 26***91 | Insert-Threaded; (M16x2-Thd) | 6 |
| 28***02 | Plug | 3 |
| 28***04 | Plug | 2 |
270-1630 Cover Gp-Access -Fuel Priming Pump
| 23***82 | Cover | 1 |
| 23***93 | Insert | 1 |
| 23***93 | Bolt-Flange Head; (M6x1x35-mm) | 6 |
257-8663 Cover Gp-Transmission
| 09***80 | Pin | 1 |
| 15***63 | Seal-O-Ring | 1 |
| 16***07 | Ring-Seal | 1 |
256-7183 Support Gp-Transmission -Charge Pump
| 25***83 | Support Group-Transmission; -Charge Pump | 1 |
| 25***46 | Support As-Front | 1 |
| 25***48 | Pump-Crescent | 1 |
279-9353 Support Gp-Transmission -Charge Pump
| 25***57 | Plate-Support | 1 |
| 25***58 | Bearing-Needle | 1 |
| 27***47 | Sleeve | 1 |
Transmission Input
290-0363 Fastener Gp-Coupling
| 29***63 | Fastener Group-Coupling | 1 |
| 9Y***34 | Bolt-Locking; (M12x1.75x45-mm) | 8 |
290-0372 Fastener Gp-Coupling
| 29***72 | Fastener Group-Coupling | 1 |
| 8T***60 | Washer-Hard (For Use With 7/16 In Bolts) | 12 |
| 8T***16 | Bolt-Plt; (7/16unc X 1 1/2) | 12 |
290-0371 Fastener Gp-Coupling
| 29***71 | Fastener Group-Coupling | 1 |
| 8T***21 | Washer-Hard; (11x21x2.5-mm Thk)(M10x1.50x30mm) | 12 |
| 8T***96 | Capscrew; (Hex Hd) (M10 X1.5 X 35, Gr10.9, Z) | 12 |
290-0365 Fastener Gp-Coupling -Flex Plate
| 29***65 | Fastener Group-Coupling; -Flex Plate | 1 |
| 9X***57 | Bolt; (M16x2x50-mm)(Locking) | 8 |
295-8478 Housing Gp-Torque Converter
| 1T***32 | Seal-O-Ring; (234.54mm Id) | 1 |
| 27***66 | Cover | 2 |
| 27***22 | Gear; (57-Teeth) | 1 |
308-2689 Housing Gp-Torque Converter
| 1T***32 | Seal-O-Ring; (234.54mm Id) | 1 |
| 27***66 | Cover | 2 |
| 27***22 | Gear; (57-Teeth) | 1 |
256-6344 Housing Gp-Torque Converter
| 25***44 | Housing Group-Torque Converter | 1 |
| 25***79 | Housing-Torque Converter | 1 |
| 28***12 | Bolt; (M10x1.5x75-mm) | 11 |
308-2093 Plate Gp-Drive
| 30***87 | Plate-Coupling | 2 |
| 30***88 | Adapter-Crankshaft | 1 |
| 30***89 | Washer | 1 |
308-2094 Plate Gp-Drive
| 16***87 | Gear-Flywheel; (134-Teeth)(Id 405.14mm) | 1 |
| 30***87 | Plate-Coupling | 2 |
| 30***88 | Adapter-Crankshaft | 1 |
283-6300 Plate Gp-Drive
| 26***57 | Adapter As-Drive | 1 |
| 26***59 | Plate As | 1 |
| 26***62 | Adapter | 1 |
265-3154 Plate Gp-Drive
| 16***87 | Gear-Flywheel; (134-Teeth)(Id 405.14mm) | 1 |
| 25***67 | Plate As | 1 |
| 25***68 | Adapter-Crankshaft | 1 |
265-3156 Plate Gp-Drive
| 26***56 | Plate Group-Drive | 1 |
| 26***54 | Adapter | 1 |
| 28***00 | Plate Group-Drive | 1 |
265-3165 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
268-5571 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
258-5673 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
268-5572 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
273-7215 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
273-7216 Torque Converter Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 10 |
| 1W***64 | Gear-Flywheel Ring; (126-Teeth) | 1 |
| 23***93 | Screw-Flat Head; (M6x1x12-mm) | 4 |
Transmission Oil System
271-3436 Control Gp-Transmission Hyd
| 10***19 | Seal-O-Ring | 1 |
| 12***73 | Cap-Connector | 1 |
| 13***89 | Clip; (Ladder) | 14 |
315-5061 Control Gp-Transmission Hyd
| 03***42 | Seal-O-Ring; (11.89mm Id) | 13 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***19 | Seal-O-Ring | 1 |
325-8599 Control Gp-Transmission Hyd
| 10***19 | Seal-O-Ring | 1 |
| 12***73 | Cap-Connector | 1 |
| 13***89 | Clip; (Ladder) | 14 |
280-1104 Control Gp-Transmission Hyd
| 03***42 | Seal-O-Ring; (11.89mm Id) | 13 |
| 10***19 | Seal-O-Ring | 1 |
| 12***73 | Cap-Connector | 1 |
325-8596 Control Gp-Transmission Hyd
| 10***19 | Seal-O-Ring | 1 |
| 12***73 | Cap-Connector | 1 |
| 13***89 | Clip; (Ladder) | 14 |
315-5063 Control Gp-Transmission Hyd
| 03***42 | Seal-O-Ring; (11.89mm Id) | 13 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***19 | Seal-O-Ring | 1 |
317-8139 Filler Gp-Power Train Oil
| 27***76 | Gauge-Oil Level (Dipstick); (Transmission) | 1 |
| 27***47 | Tube As | 1 |
| 31***39 | Filler Group-Power Train Oil | 1 |
285-7632 Filter & Mtg Gp-Oil -Transmission
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
264-6353 Filter & Mtg Gp-Oil -Transmission
| 06***61 | Seal-O-Ring (Id=40.87mm) | 2 |
| 12***17 | Filter-Oil; (Ultra High Efficiency)(Hydraulic, Transmission) | 1 |
| 18***64 | Valve As-Fluid Sampling; (Transmission) | 1 |
320-3067 Filter & Mtg Gp-Oil
| 06***61 | Seal-O-Ring (Id=40.87mm) | 2 |
| 18***08 | Plug As; (High Temperature) | 1 |
| 18***64 | Valve As-Fluid Sampling; (Transmission) | 1 |
325-8607 Filter Gp-Oil -Transmission
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 14***09 | Plug As-Sto | 2 |
310-2972 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
276-5296 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
325-8606 Filter Gp-Oil -Transmission
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 14***09 | Plug As-Sto | 2 |
285-7630 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
325-8605 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***28 | Filter-Oil; (Ultra High Efficiency) | 1 |
325-8604 Filter Gp-Oil -Transmission
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 12***15 | Filter-Oil; (Ultra High Efficiency)(Transmission) | 2 |
280-8630 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***28 | Filter-Oil; (Ultra High Efficiency) | 1 |
285-7631 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
314-4080 Filter Gp-Oil
| 03***42 | Seal-O-Ring; (11.89mm Id) | 1 |
| 06***38 | Seal-O-Ring; (7.65 mm Id) | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
278-2566 Manifold Gp-Control -Shallow Sump
| 10***62 | Dowel | 2 |
| 18***78 | Valve Group-Relief; (Torque Converter Inlet) | 1 |
| 19***52 | Valve-Relief; (Clutch Back Pressure) | 1 |
325-8594 Manifold Gp-Control
| 10***62 | Dowel | 2 |
| 14***09 | Plug As-Sto | 2 |
| 18***78 | Valve Group-Relief; (Torque Converter Inlet) | 1 |
325-8595 Manifold Gp-Control
| 10***62 | Dowel | 2 |
| 14***09 | Plug As-Sto | 2 |
| 18***78 | Valve Group-Relief; (Torque Converter Inlet) | 1 |
280-1105 Manifold Gp-Control
| 10***62 | Dowel | 2 |
| 18***78 | Valve Group-Relief; (Torque Converter Inlet) | 1 |
| 19***52 | Valve-Relief; (Clutch Back Pressure) | 1 |
325-8593 Valve Gp-Transmission Control
| 25***49 | Spring; (Lube Bypass) | 1 |
| 26***84 | Spring; (Pressure Regulator) | 1 |
| 26***85 | Spring; (Torque Converter) | 1 |
260-3494 Valve Gp-Transmission Control
| 25***49 | Spring; (Lube Bypass) | 1 |
| 25***50 | Cover-Valve | 1 |
| 25***51 | Spool-Bypass; (Torque Converter) | 1 |
Transmission Output
285-1195 Yoke Gp
| 16***81 | Bolt; (M16x2x75-mm) | 1 |
| 27***52 | Yoke-Output | 1 |
| 28***95 | Yoke Group | 1 |
311-1395 Yoke Gp
| 16***81 | Bolt; (M16x2x75-mm) | 1 |
| 31***94 | Yoke (7c) | 1 |
| 31***95 | Yoke Group | 1 |
271-3434 Yoke Gp
| 16***81 | Bolt; (M16x2x75-mm) | 1 |
| 25***47 | Yoke-Output | 1 |
| 27***34 | Yoke Group | 1 |
308-4572 Yoke Gp
| 16***81 | Bolt; (M16x2x75-mm) | 1 |
| 30***71 | Yoke | 1 |
| 30***72 | Yoke Group | 1 |
285-1196 Yoke Gp
| 16***81 | Bolt; (M16x2x75-mm) | 1 |
| 27***53 | Yoke-Output | 1 |
| 28***96 | Yoke Group | 1 |
CX28 serial number reference
The CX28 carries its own ID/serial tag on the transmission housing (near the bellhousing or top of the case), separate from the truck or coach chassis PIN plate; the host vehicle's build sheet or chassis plate will usually cross-reference the transmission model and serial. Read the tag as the transmission model (CX28) followed by its serial number: a 3-character prefix plus a numeric sequence (for example T3X00624). The prefix identifies the production/build series of the transmission itself; quote the full prefix plus digits, not the prefix alone, when ordering parts or pulling service history.
| Prefix | Identifies | Notes |
|---|---|---|
| T3X | CX28 on-highway transmission (medium-duty vocational trucks, buses, RV/motorhome chassis) | Six-speed electronically controlled planetary automatic transmission, rated up to 298 kW (400 hp) and 1,695 N·m (1,250 lb-ft), paired behind a Cat C7 or C9 diesel. Carries three power take-off locations: two on the torque converter housing (2 and 8 o'clock) plus a high-output drive at the rear for a live yoke, direct-drive pump, or clutched adapter. This prefix appears on the transmission's own service literature and on individually tagged units, not on the host vehicle's chassis PIN. |
Frequently asked questions
What engine does the Cat CX28 use?
The CX28 isn't an engine — it's Caterpillar's six-speed automatic on-highway transmission, paired with the Cat C7 (7.2 L) or C9 (8.8 L) diesel rated up to 298 kW (400 hp) and 1695 N·m (1250 lb-ft) of torque. The militarized Caiman MRAP chassis version pairs it with a 336 kW (450 hp) C9.
What is the operating weight?
Caterpillar does not publish a standalone CX28 weight. Its larger CX31 and CX35 siblings, built in the same aluminum-case family, run about 420 to 510 kg (925 to 1125 lb) with rear PTO fitted, so the CX28 — the smallest of the three — falls below that range. Confirm the exact figure for a given unit with a Cat dealer.
What replaced the Cat CX28?
Nothing directly. Caterpillar exited the US on-highway diesel engine business in 2010 and wound down its vocational truck line by 2016, ending the C7/C9 on-highway production the CX28 depended on. Unlike the CX31 and CX35, which continue today as CX31-P600 and CX35-P800 well-service transmissions, Cat never released a CX28 oilfield variant, so surviving units are legacy stock supported through dealer parts channels rather than an active product line.
What CX28 owners discuss
How does the CX28 actually shift in daily driving compared to an Allison?
The CX28 is a six-speed planetary automatic built to bolt in behind a C7 or C9 diesel for on-highway trucks and motorcoach chassis, not a stand-alone unit. Field impressions of the Cat on-highway automatic line describe shifts as smooth and well matched to load through most of the range, with an occasional firm 2-to-1 downshift reported under a hard throttle stab from a rolling stop. Because far fewer trucks and coaches left the factory with this box than with an Allison, there is no large body of long-term owner experience to compare against - treat any single account as anecdotal rather than a fleet-wide verdict.
Does the CX28 use a torque-converter lockup clutch, and does it cause problems?
Yes. Like the rest of the Cat CX on-highway family it is a torque-converter automatic with an electronically commanded lockup clutch that engages in the higher gears to cut slip and improve highway economy. On units brought in for a shifting complaint, lockup clutch engagement is one of the first things checked alongside sensor and pedal-calibration faults, because a clutch that will not release, or will not lock, produces the same drivability symptoms as an electronic fault. Confirm lockup clutch operation as part of the diagnostic routine rather than assuming it is fine - have your dealer verify with the proper diagnostic tool.
What's the most common shifting complaint reported on the CX28?
The recurring symptom is a transmission that will only move in first gear and reverse and never advances to second, third, or higher - effectively stuck in a default low range. The pattern most often traces back to a bad or missing output speed sensor signal reaching the transmission control module; without a valid signal the controller has no basis to command an upshift. Other items on the same troubleshooting list include an incompletely plumbed oil cooling circuit (heat exchanger or auxiliary fan disconnected or bypassed), lockup clutch engagement, accelerator pedal calibration, and transmission oil pressure. This is a drivability and safety issue on a road vehicle - have your dealer verify the diagnosis before returning it to service.
Can the electronic side of the CX28 be diagnosed with a generic scan tool?
Not reliably. Pulling and interpreting diagnostic codes on this transmission's control module is described as requiring Caterpillar's own electronic service tool; there is no generic code reader or aftermarket handheld equivalent that reliably reads this system. A dash that looks clean on a cheap reader does not rule out an active fault such as a bad output speed sensor signal. Anyone chasing an intermittent shift complaint should plan on a shop with the proper Cat diagnostic software rather than a general-purpose OBD tool.
Is service on the CX28 (fluid, filter, cooling circuit) any different from other Cat on-highway automatics?
The basics are the same as other Cat on-highway planetary automatics: scheduled fluid and filter service on interval, using the fluid specification called for by the transmission rather than substituting whatever is on hand. What comes up repeatedly in shifting-complaint discussions is the external oil cooling circuit - the heat exchanger and any auxiliary cooling fan need to be fully connected and functional, because a bypassed or disconnected cooling loop has turned up on units that were also throwing shift complaints, and it can mask or mimic an electronic fault. The case also carries provision for a power take-off, so on trucks fitted with an aftermarket PTO, confirm the drain and fill routing and fluid level have not been affected by that install.
Why is parts and service support for the CX28 thinner than for an Allison-equipped truck?
Cat stopped selling on-highway diesel engines in the US at the end of 2009 rather than certify the C7/C9 line to 2010 emissions rules, and that ended new-truck sales of the transmission built specifically around those engines. Cat continued factory support for the engines already in the field, but the on-highway automatic transmission line moved to a separate manufacturing partner rather than staying inside the mainstream Cat highway dealer network. Practically, that means fewer trucks and coaches running this transmission today, less shop familiarity with it than with an Allison, and code-level diagnostic work still needs to route through someone equipped with the correct Cat-based diagnostic software.
What should I check before buying a used truck or motorcoach fitted with a CX28?
Cycle through all six forward gears on a test drive and confirm there is no hunting, flare, or hesitation, paying particular attention to the 1-2 and 2-1 shifts. Ask for a code pull with the proper Cat diagnostic tool rather than relying on a generic reader - a clean-looking dash does not rule out an active output speed sensor fault. Inspect the external transmission oil cooler and any auxiliary cooling fan for signs of a prior bypass or disconnection. Check fluid level, condition, and service records, and confirm exactly which engine, C7 or C9, it is actually paired with, since that affects parts sourcing and duty-cycle expectations. Factor in that this transmission's support network is thinner than Allison's, so line up a shop with the right diagnostic software before you need one. Have a qualified dealer or transmission shop verify condition before purchase.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Serial-range & configuration variants
This page covers the Caterpillar CX28. Related factory variants of the same model family:
CX28
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