Caterpillarengine - trucktransmission-onhighway
Caterpillar CX35
Maintenance schedule, common problems & OEM parts breakdown
The Cat CX35 is an eight-speed, on-highway automatic transmission with a lockup torque converter and full electronic controls, not a standalone machine or engine. It is the heavy-duty member of Caterpillar's CX-series on-highway transmission line alongside the smaller CX28 and six-speed CX31, and it pairs behind a customer-specified Cat engine rather than carrying its own powerplant, most commonly the C15 in on-highway configuration. An aluminum case trims weight well below the off-road CX-series variants it derives from; a rear-PTO-equipped CX35 weighs about 510 kg (1,125 lb). Up to four PTO mounting locations are offered, including two optional rear PTOs rated to roughly 149 kW (200 hp) each. The transmission saw its main on-highway use in Caterpillar's own CT660/CT680/CT681 vocational truck line, targeting the heaviest dump, mixer, and severe-duty vocational applications that needed more torque capacity than the CX31 could handle.
What sets the CX35 apart from its CX28 and CX31 siblings is clutch size and torque capacity: the number in each transmission's name is its clutch diameter in centimeters, and the CX35's larger 35 cm clutch pack lets it carry engine ratings up to roughly 466 kW (625 hp) and 2,779 Nm (2,050 lb-ft), well above the CX31's ceiling. That capacity made it the transmission of choice for the highest-torque vocational trucks Caterpillar built before exiting the on-highway vocational truck business in early 2016. In today's used and parts market, CX35 units turn up mainly as take-outs, rebuilds, and support parts for surviving CT660/CT680/CT681 trucks and other severe-duty vocational chassis built during that window; because the on-highway program was short-lived, sourcing hinges more on transmission specialists and dealer parts support than on broad aftermarket coverage, so confirm parts and rebuild kit availability against the specific serial and PTO configuration before committing to a repair.
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 CX35 specifications
Engine
| Transmission type | Cat CX35 — 8-speed automatic on-highway/vocational transmission with lock-up torque converter, wet clutches, and planetary gearsets under electronic control. Aluminum case. The "35" designation refers to the 35 cm clutch diameter. |
| Compatible engine power | Rated for engines producing up to 466 kW (625 hp). |
| Compatible engine torque | Rated for engine torque up to 2779 N·m (2050 lb-ft). |
| Displacement / cylinders / emissions tier | Not applicable. CX35 is an automatic transmission, not an engine. In vocational truck applications it is factory-paired behind Cat C15 on-highway diesel engines; the engine's own displacement, cylinder count, and emissions tier are not transmission specifications. |
Weights
| Transmission weight (with rear-mount PTO) | Approx. 510 kg (1,125 lb). |
| Vehicle / operating weight | Not applicable. CX35 is a driveline component, not a complete chassis or machine — operating weight belongs to the host truck it is installed in. |
Dimensions
| Case and mounting | Aluminum case; 8-bolt SAE flywheel-housing mounting pattern. Exterior-mounted solenoids allow service without removing the oil pan. |
| Overall transmission envelope (length/width/height) | Not published in available trade or dealer literature for this unit. Confirm with a Cat on-highway dealer for the exact case and PTO configuration fitted. |
Performance
| Forward / reverse speeds | 8 forward speeds, 1 reverse. 6th gear is 1:1 direct drive; 7th and 8th are overdrive ratios. |
| Approximate gear ratio spread | Roughly 5.7:1 in 1st down to about 0.63:1 in 8th (overdrive); intermediate ratios vary by published source — treat as approximate. |
| PTO capability | Multiple PTO mounting locations depending on configuration, including rear-mount PTO capacity in the 149-224 kW (200-300 hp) range. Exact location count and per-PTO rating vary by source and by which PTO options are ordered. |
| Gradeability / drawbar / dig-dump performance | Not applicable. CX35 is a driveline component — these figures are properties of the host truck chassis and axle/tire package, not the transmission itself. |
Service capacities (summary)
| Transmission fluid | Cat ATF-HD2 automatic transmission fluid, built to the Cat AT-1 performance spec — not Cat TDTO — with a transmission- or remote-mounted spin-on filter. Exact fill capacity is not published for this configuration — verify with a Cat on-highway dealer. |
| Fuel tank / engine oil / cooling system | Not applicable. CX35 is a transmission, not a complete engine or truck; fuel, engine-oil, and cooling-system capacities belong to the host vehicle's engine, not this component. |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
CX35 fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| On-highway automatic transmission (CX35) | Not published in Caterpillar's public fluids literature for this unit; sump volume varies with PTO count, retarder option, and transmission- vs. remote-mounted oil filter configuration. Confirm exact fill volume with a Cat dealer or the vehicle-specific OMM. | Cat ATF-HD2, a synthetic automatic transmission fluid built to the Cat AT-1 performance spec, is the factory-preferred fluid for the CX35 and is not interchangeable with Cat TDTO fluids used in powershift transmissions. Acceptable commercial alternatives must meet Cat AT-1, Dexron-III(H), Dexron IV, or Dexron VI requirements. Rated operating range is roughly -23 C to 45 C (-10 F to 113 F); below -23 C (-10 F), warm the engine about 20 minutes before engaging drive, or fit a properly sized transmission oil heater, before duty-cycle operation in cold climates. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar CX35 maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 6,000 h |
|
Servicing the CX35 beyond the schedule
Predictive Maintenance & Fluid Analysis
Track the CX35 through scheduled Cat ATF-HD2 (AT-1 spec) fluid sampling rather than fluid changes on the calendar alone. Trending particulate count and wear metals in the sample flags clutch pack and torque converter wear before it shows up as a shift complaint. Watch breather condition and cooler line integrity alongside the sample results, since a restricted breather or a leaking cooler line accelerates fluid degradation and skews sample readings on this transmission.
Corrective & Common Repairs
Most CX35 driveability complaints trace to two sources: clutch-solenoid related gear slip or hesitant shifts, and TCM communication faults caused by corroded or loose harness connectors between the transmission-mounted TCM, the engine ECM, and chassis grounds. Before condemning the TCM or a clutch solenoid, verify connector pin tension and ground integrity along the full harness run; a poor connection at any joint can mimic an internal transmission fault.
Overhaul & Rebuild Points
Overhaul work on the CX35 centers on the clutch packs, the torque converter lockup clutch, and the converter lip seal. Caterpillar issued an updated bolt-and-washer fastening procedure for the pilot-to-lockup-clutch-housing joint on CX31 and CX35 units, so confirm the current hardware and torque spec before reassembly. Inspect internal bushings and the engine-driven pump drive at the same time, since the pump also supplies transmission lubrication.
Seasonal & Environment Servicing
Because the transmission's hydraulic pump is engine-driven, its lubrication and shift quality depend on the engine reaching operating speed and temperature first. In cold weather, idle the engine and let fluid come up to temperature before applying PTO load or heavy pulls, and check the breather for ice or moisture blockage. On stationary high-load PTO work such as pumping or mixing, avoid prolonged operation with the converter unlocked, which raises fluid temperature faster than road driving does.
CX35 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 → |
| 7X-6312 | Cord As-Heater Element | Scheduled service item | Check fitment → |
| 127-8609 | Cord As-Heater Element | Scheduled service item | Check fitment → |
| 8S-9129 | Filter-Magnetic | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
CX35 fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| OT (RED warning lamp) | Transmission oil over-temperature warning shown on the shift-selector pad, paired with the RED driver-warning lamp. | Sustained lugging or steep-grade operation, undersized/plugged transmission oil cooler, low coolant flow through the cooler, or the truck left in gear with the parking brake applied instead of neutral. | Stop, let the transmission cool, verify cooler airflow and coolant flow are not restricted, confirm the auto-neutral/parking-brake interlock is enabled, and check fluid level and condition before returning to service. |
| LO (RED warning lamp) | Transmission oil level low warning on the shift pad, paired with the RED lamp. | Low fluid from a leak (seals, cooler lines, fill plug) or fluid not topped off after a filter/service event; on this transmission there is no dipstick, fluid is checked via the electronic level-check routine. | Run the shift-pad electronic oil level check with engine at operating temperature per the routine, add Cat-approved automatic transmission fluid to bring level into range, and inspect for external leaks. |
| OL / OL-OK (shift-pad oil level check) | Result message from the driver-initiated electronic oil level check function on the shift selector pad; OL-OK confirms fluid level is correct, other OL messages indicate level is out of range. | Normal confirmation after a level check, or an out-of-range result caused by low/high fluid, a level-check performed at the wrong temperature/RPM, or a faulty level sensor. | Follow the shift-pad prompts exactly (engine warm, in neutral, at specified idle) and read the resulting message; if a non-OK message repeats after correcting fluid level, have the level sensor circuit checked. |
| AMBER diagnostic lamp (active code stored) | General trouble indicator showing the transmission ECM has an active or logged diagnostic code in its electronic control system; the amber lamp itself does not identify which fault. | Any sensor, solenoid, wiring, or ECM-detected fault in the power-train electronic control system. | Connect Cat Electronic Technician (Cat ET) at the diagnostic connector to read the specific SPN-FMI code(s) stored, then service per the identified fault. |
| SPN 3027 | Transmission fluid level circuit fault, tied to the low-oil condition reported on the shift pad. | Level sensor signal out of range, damaged sensor wiring/connector, or genuinely low fluid. | Check fluid level electronically, inspect sensor wiring and connector for damage or corrosion, and replace the level sensor if the circuit reads incorrectly with fluid confirmed at proper level. |
| SPN 177 | Transmission oil temperature circuit fault or high-temperature indication feeding the OT warning. | Cooling system restriction, undersized cooler for the application, sustained high-load operation, or a faulty temperature sensor/circuit. | Verify actual oil temperature with a hand-held reference, inspect cooler and lines for restriction, and check sensor wiring before condemning the sensor. |
| FMI 14 - output speed sensor disagreement | The ECM compares two transmission output speed sensors against each other and against a calculated output speed (from input speed, countershaft speed, and axle speed over the data link); if they disagree or read near zero when they should not for several seconds, this code sets. | A loose or failed output speed sensor, damaged tone-ring/sensor gap, or wiring fault between a sensor and the ECM. | Inspect both output speed sensors and connectors, check sensor air gap and mounting, then verify readings on Cat ET before replacing a sensor. |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
CX35 attachments & work tools
Machine type note
CX35 is an eight-speed on-highway vocational automatic transmission with lockup torque converter and electronic controls, not an implement-carrying machine. It has no bucket/blade/hammer-style work-tool line; its configurable options are PTOs, pump drives, and a retarder.
Engine pairing / duty rating
Matches Cat C15 engine ratings up to 466 kW (625 hp) and 2779 Nm (2,050 lb-ft) torque for heavy vocational truck duty. Ratings vary by chassis and application; verify against the specific truck build sheet.
PTO (power take-off) locations
Up to four PTO mounting locations are offered, including two optional rear PTOs rated to roughly 149 kW (200 hp) each. Exact PTO count and location depend on the ordered transmission configuration.
Integral pump drive options
Optional integral pump drive arrangements add SAE B and SAE C direct-mount pads for hydraulic pumps, letting body/equipment builders mount pumps straight on the transmission instead of through a separate PTO gearbox.
Retarder option
An optional hydraulic retarder can be specified for supplemental vehicle braking on heavy vocational duty cycles. It is a factory-order option, not a field-installed attachment.
Oil filter and mounting arrangement
Offered with either a transmission-mounted or remote-mounted oil filter, chosen to suit chassis packaging. This is a build-configuration option rather than a work tool.
All CX35 assemblies by section
Every catalogued assembly group for the Caterpillar CX35. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Basic Transmission
277-0450 Planetary Gp-Transmission
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***28 | Seal-O-Ring | 8 |
| 0T***00 | Plug (.5625" Diameter) | 1 |
292-4359 Planetary Gp-Transmission
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 0T***00 | Plug (.5625" Diameter) | 1 |
| 13***61 | Plate-Clutch | 5 |
294-2724 Planetary Gp-Transmission
| 03***28 | Seal-O-Ring | 7 |
| 0T***00 | Plug (.5625" Diameter) | 1 |
| 13***61 | Plate-Clutch | 5 |
294-2721 Transmission Ar
| 27***48 | Cover Group-Transmission; -Pump Drive | 1 |
| 27***48 | Pump Group-Gear | 1 |
| 27***50 | Planetary Group-Transmission | 1 |
294-2711 Transmission Ar
| 27***48 | Cover Group-Transmission; -Pump Drive | 1 |
| 27***48 | Pump Group-Gear | 1 |
| 29***11 | Transmission Ar | 1 |
294-2701 Transmission Ar -8-Speed
| 27***48 | Cover Group-Transmission; -Pump Drive | 1 |
| 29***45 | Housing Group-Torque Converter | 1 |
| 29***59 | Planetary Group-Transmission | 1 |
316-6382 Transmission Ar-Complete -8-Speed
| 25***65 | Cover Group-Shipping | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
299-2460 Transmission Ar-Complete -8-Speed
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
| 27***45 | Drive Group-Pump; -Rear Power Take-Off | 1 |
299-2500 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
322-7174 Transmission Ar-Complete -8-Speed
| 25***65 | Cover Group-Shipping | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
294-2725 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
313-9376 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
324-9067 Transmission Ar-Complete -8-Speed
| 25***65 | Cover Group-Shipping | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
299-2470 Transmission Ar-Complete -8-Speed
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
| 27***23 | Torque Converter Group | 1 |
316-2540 Transmission Ar-Complete
| 23***97 | Core Group-Oil Cooler | 1 |
| 29***60 | Control Group-Transmission; -Keypad Shifter | 1 |
| 31***40 | Transmission Ar-Complete | 1 |
299-2508 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
299-2510 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
300-5629 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
299-2509 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
294-2715 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
299-2446 Transmission Ar-Complete -8-Speed
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
| 27***45 | Drive Group-Pump; -Rear Power Take-Off | 1 |
294-2700 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 0 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
294-2720 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***52 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***41 | Yoke Group | 1 |
287-5739 Transmission Ar-Complete -8-Speed
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
| 27***46 | Pan Group-Transmission Oil | 1 |
299-2507 Transmission Ar-Complete -8-Speed
| 13***27 | Cap-Fill; (Power Train Oil) | 1 |
| 26***53 | Filter & Mtg Group-Oil; -Transmission | 1 |
| 27***42 | Yoke Group | 1 |
Cooling System
287-6593 Core Gp-Oil Cooler
| 21***95 | Seal-O-Ring | 2 |
| 23***96 | Core As-Oil Cooler; (Transmission) | 1 |
| 23***55 | Bonnet | 1 |
294-0948 Core Gp-Oil Cooler
| 10***01 | Gasket | 2 |
| 29***46 | Bonnet | 2 |
| 29***59 | Flange | 2 |
238-7997 Core Gp-Oil Cooler
| 21***95 | Seal-O-Ring | 2 |
| 23***96 | Core As-Oil Cooler; (Transmission) | 1 |
| 23***97 | Core Group-Oil Cooler | 1 |
211-5860 Core Gp-Oil Cooler
| 0S***95 | Bolt 1.25 In. (31.75 mm) Long Guard Assemblies To Radiator Guard | 16 |
| 21***75 | Core As-Oil Cooler; (Transmission) | 1 |
| 21***60 | Core Group-Oil Cooler | 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 |
299-2501 Electronics Gp-Power Train
| 29***56 | Software Group-Power Train | 1 |
| 29***57 | Service Group-Power Train | 1 |
| 29***01 | Electronics Group-Power Train | 1 |
312-8413 Electronics Gp-Power Train
| 31***13 | Electronics Group-Power Train | 1 |
| 32***97 | Software Group-Power Train | 1 |
| 32***98 | Service Group-Power Train | 1 |
312-8411 Electronics Gp-Power Train
| 31***11 | Electronics Group-Power Train | 1 |
| 33***09 | Software Group-Power Train | 1 |
| 33***10 | Service Group-Power Train | 1 |
332-4747 Heater As-Fluid
| 13***17 | Cap As-Dust | 1 |
| 33***47 | Heater As-Fluid | 1 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 1 |
332-4746 Heater As-Fluid
| 13***17 | Cap As-Dust | 1 |
| 33***46 | Heater As-Fluid | 1 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 1 |
332-6777 Heater Gp-Fluid
| 33***46 | Heater As-Fluid | 1 |
| 33***77 | Heater Group-Fluid | 1 |
| 7X***12 | Cord As-Heater Element; -120-Volt | 1 |
332-6778 Heater Gp-Fluid
| 12***09 | Cord As-Heater Element; -240-Volt | 1 |
| 33***47 | Heater As-Fluid | 1 |
| 33***78 | Heater Group-Fluid | 1 |
4p-5820 Sensor Gp-Speed -Crankshaft
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 2 |
| 17***49 | Strap; (Marker) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 2 |
196-1185 Sensor Gp-Speed
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
| 17***49 | Strap; (Marker) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 2 |
164-7577 Switch Gp-Bypass -Transmission Oil
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
| 16***77 | Switch Group-Bypass; -Xmsn Lubrication Supply Filter-Xmsn Lubrication Charge Filter-Hoist Screen-Tc, Front Brake Cooling-Transmission Oil Filter-Rear Axle Oil Filter | 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 |
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
250-5765 Cover Gp-Shipping
| 25***65 | Cover Group-Shipping | 1 |
| 30***24 | Clamp As | 3 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 2 |
271-0448 Cover Gp-Transmission -Pump Drive
| 22***81 | Film-Warning; -Universal | 2 |
| 27***66 | Cover | 2 |
| 27***47 | Cover | 1 |
294-2716 Pan Gp-Transmission Oil
| 18***98 | Connector As | 2 |
| 23***82 | Seal-O-Ring | 1 |
| 23***84 | Seal; (35.6mm Od) | 1 |
277-0446 Pan Gp-Transmission Oil
| 18***98 | Connector As | 2 |
| 23***82 | Seal-O-Ring | 1 |
| 23***84 | Seal; (35.6mm Od) | 1 |
299-2452 Pan Gp-Transmission Oil
| 00***62 | Seal-O-Ring; (63.17mm Id) | 2 |
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***36 | Seal-O-Ring | 1 |
292-4357 Pan Gp-Transmission Oil
| 00***62 | Seal-O-Ring; (63.17mm Id) | 2 |
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***36 | Seal-O-Ring | 1 |
294-2695 Pan Gp-Transmission Oil
| 18***98 | Connector As | 2 |
| 23***82 | Seal-O-Ring | 1 |
| 23***84 | Seal; (35.6mm Od) | 1 |
293-4695 Plug Gp-Shipping -Remote Mounted Filter
| 29***95 | Plug Group-Shipping; -Remote Mounted Filter | 1 |
| 5P***01 | Seal-O-Ring; (29.74mm Id)(Pump To Fitting As) | 2 |
| 9S***81 | Plug-Straight Thread; (Straight Thread O-Ring) | 2 |
Transmission Input
294-2680 Drive Gp-Pump -Rear
| 09***16 | Ring-Retaining; (External) | 1 |
| 29***80 | Drive Group-Pump; -Rear | 1 |
| 29***81 | Shaft As | 1 |
277-0445 Drive Gp-Pump -Rear Pto
| 09***16 | Ring-Retaining; (External) | 1 |
| 27***22 | Shaft As; (Rear Power Take-Off) | 1 |
| 27***45 | Drive Group-Pump; -Rear Power Take-Off | 1 |
289-9549 Fastener Gp-Coupling
| 09***70 | Bolt-Socket Hd; (M12 X 1.75 X 45) | 12 |
| 28***49 | Fastener Group-Coupling; -Transmission | 1 |
294-2712 Housing Gp-Torque Converter
| 13***78 | Seal-O-Ring | 1 |
| 16***50 | Bolt; (M12x1.75x65-mm) | 13 |
| 1A***23 | Dowel (1" Long) | 1 |
292-4345 Housing Gp-Torque Converter
| 09***58 | Bolt; (Socket Head) (M10x1.5x70mm) | 13 |
| 12***63 | Ring-Seal | 2 |
| 13***78 | Seal-O-Ring | 1 |
294-2722 Housing Gp-Torque Converter
| 13***78 | Seal-O-Ring | 1 |
| 16***50 | Bolt; (M12x1.75x65-mm) | 13 |
| 1A***23 | Dowel (1" Long) | 1 |
284-3606 Plate Gp-Drive
| 25***51 | Gear-Flywheel; (113-Teeth) | 1 |
| 28***97 | Plate-Washer | 1 |
| 28***98 | Plate-Flexible | 5 |
277-5423 Torque Converter Gp
| 09***70 | Bolt-Socket Hd; (M12 X 1.75 X 45) | 8 |
| 12***94 | Seal-O-Ring | 1 |
| 12***10 | Seal-O-Ring | 1 |
288-2663 Torque Converter Gp
| 09***70 | Bolt-Socket Hd; (M12 X 1.75 X 45) | 8 |
| 12***94 | Seal-O-Ring | 1 |
| 12***10 | Seal-O-Ring | 1 |
Transmission Oil System
299-2471 Control Gp-Transmission Hyd
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***28 | Seal-O-Ring | 3 |
| 10***04 | Kit-Receptacle; (4-Pin)(Start Switch) | 1 |
292-4354 Control Gp-Transmission Hyd
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***28 | Seal-O-Ring | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
277-0447 Control Gp-Transmission Hyd
| 03***53 | Seal-O-Ring; (08.92mm Id) | 1 |
| 03***28 | Seal-O-Ring | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
277-0444 Control Gp-Transmission Hyd
| 03***28 | Seal-O-Ring | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
| 11***43 | Sleeve-Plastic; (32-mm Dia)(240-cm) | 0 |
299-2451 Control Gp-Transmission Hyd
| 03***28 | Seal-O-Ring | 3 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 1 |
| 10***20 | Seal-O-Ring | 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 |
263-5052 Filter & Mtg Gp-Oil -Transmission
| 06***61 | Seal-O-Ring (Id=40.87mm) | 2 |
| 18***08 | Plug As; (High Temperature) | 1 |
| 18***64 | Valve As-Fluid Sampling; (Transmission) | 1 |
304-8988 Gauge Gp-Oil Level (Dipstick)
| 23***35 | Seal-O-Ring | 1 |
| 29***17 | Adapter | 1 |
| 29***52 | Clamp | 1 |
289-5201 Manifold Gp-Control -Tmsn Modulator Control
| 14***74 | Spring | 6 |
| 18***84 | Piston | 6 |
| 18***85 | Spring | 6 |
277-0448 Pump Gp-Gear
| 10***86 | Seal-O-Ring | 2 |
| 16***42 | Bolt; (M10x1.5x55-mm) | 2 |
| 27***29 | Tube As | 1 |
292-4360 Pump Gp-Gear
| 10***86 | Seal-O-Ring | 2 |
| 28***61 | Pump Group-Gear | 1 |
| 29***60 | Pump Group-Gear | 1 |
284-4661 Pump Gp-Gear
| 09***58 | Bolt; (Socket Head) (M10x1.5x70mm) | 4 |
| 12***36 | Bearing-Sleeve | 1 |
| 26***51 | Body As-Pump | 1 |
244-7772 Valve Gp-Modulating -Transmission Clutch, Ecpc
| 16***08 | Washer; (13.03x25.4x2.38-mm Thk) | 1 |
| 16***24 | Nut-Self-Locking; (1/2-28-Thd) | 1 |
| 24***72 | Valve Group-Modulating; -Transmission Clutch, Ecpc | 1 |
290-0596 Valve Gp-Reducing
| 29***96 | Valve Group-Reducing | 1 |
| 3K***60 | Seal Pilot Manifold On; Seal To Boom Check Valve Drain | 1 |
| 6V***52 | Cap-Dust; (Fuel Supply Tee Connection) | 1 |
325-3696 Valve Gp-Relief
| 11***50 | Cover | 2 |
| 14***79 | Spring-Compression | 1 |
| 16***77 | Switch Group-Bypass; -Xmsn Lubrication Supply Filter-Xmsn Lubrication Charge Filter-Hoist Screen-Tc, Front Brake Cooling-Transmission Oil Filter-Rear Axle Oil Filter | 1 |
277-0431 Valve Gp-Relief -Main
| 11***50 | Cover | 2 |
| 13***99 | Spring | 1 |
| 14***79 | Spring-Compression | 1 |
277-6904 Valve Gp-Retarder Hyd Control -Transmission
| 09***49 | Bolt; (M8x1.25x40-mm) | 5 |
| 14***74 | Plate | 1 |
| 18***33 | Spool | 1 |
Transmission Output
277-0441 Yoke Gp
| 27***60 | Retainer | 1 |
| 27***05 | Yoke | 1 |
| 27***41 | Yoke Group | 1 |
277-0442 Yoke Gp
| 27***60 | Retainer | 1 |
| 27***03 | Yoke | 1 |
| 27***42 | Yoke Group | 1 |
CX35 serial number reference
The serial/PIN data plate is riveted to the transmission housing (case or bell-housing area) rather than to a separate machine frame, since the CX35 is sold both as a standalone component and as an installed unit. Read the plate as a 3-character alphanumeric prefix (W3X) followed by a sequential build number; the prefix identifies the on-highway CX35 configuration, and the full prefix-plus-sequence string is what a dealer needs to pull exact parts and service history.
| Prefix | Identifies | Notes |
|---|---|---|
| W3X | CX35 On-Highway Transmission (base vocational truck unit) | Eight-speed automatic with lockup torque converter and electronic controls, for on-highway vocational trucks. Pairs chiefly with the C15 engine up to roughly 466 kW (625 hp) and 2780 N·m (2050 lb-ft) torque; also mounts to C13. Introduced around 2007. Single serial series (00001-UP) covers the whole line - converter, retarder, PTO, sump, filter, yoke and flex-plate options are read from the digits after the prefix, not from a separate prefix. |
Frequently asked questions
What engine does the Cat CX35 pair with?
The CX35 is a transmission, not an engine. It bolts up behind a customer-specified Caterpillar engine, most commonly the on-highway C15, and was factory-rated for engines up to roughly 466 kW (625 hp) and 2,779 Nm (2,050 lb-ft) of torque.
What is the CX35's operating weight?
The transmission itself weighs approximately 510 kg (1,125 lb) as fitted with a rear PTO, per Caterpillar's on-highway transmission spec sheet. Weight varies somewhat with PTO count and pump configuration, so treat this as a baseline rather than an exact figure for every build.
What replaced the Cat CX35?
There is no documented direct on-highway successor. Caterpillar exited its on-highway vocational truck program (CT660/CT680/CT681) in early 2016 and did not release a follow-on automatic transmission for that market; vocational trucks built since typically spec an Allison automatic instead. Caterpillar continued to build heavy-duty transmissions sharing CX35 architecture for well-service and oilfield applications, but those are a different duty class, not a like-for-like on-highway replacement.
What CX35 owners discuss
How does the CX35 shift and does the lockup torque converter feel different from a standard automatic?
The CX35 keeps its torque converter locked up in every forward gear, not just top gear, so drivers describe the feel as closer to a manual with well-timed shifts than a typical slushy automatic. Clutch engagement is electro-hydraulic and fully modulated, so shift quality depends heavily on solenoid condition and fluid state rather than mechanical bands. On the 8-speed CX35, sixth gear is the 1:1 direct ratio with seventh and eighth as overdrives, and that direct-drive gear is the one most often flagged when a shift starts feeling soft or slips toward neutral. A rough or delayed shift into the direct gear points first at clutch solenoid pressure, not the converter itself.
Is PTO use common on trucks fitted with the CX35, and does it affect the transmission?
Yes. The CX35 is a body-builder transmission installed behind a customer-specified engine on vocational trucks, and PTO provision for dump bodies, mixers, and similar equipment is a standard part of the package. PTO hours run independently of travel hours and dealers can pull them alongside engine hours through the truck's telematics, which is useful for judging real duty cycle on a working truck. Heavy stationary PTO use adds heat and load cycles the transmission cooler has to handle, so trucks that ran PTO hard tend to show fluid wear sooner than highway-only trucks with similar mileage.
What transmission fluid does the CX35 need, and how often should it be changed?
The CX35 calls for Cat ATF-HD2 or another fluid meeting the Cat AT-1 automatic transmission fluid specification - it is not the same fluid as the TDTO used in Cat powershift or final drive components, and using the wrong fluid class is a common mix-up on shops that also service off-highway iron. Cat's own literature says ATF-HD2 extends the drain interval well beyond a generic AT-1 fluid when paired with the scheduled filter changes and oil sampling called out in the transmission's operation and maintenance manual. Exact interval depends on duty cycle and sample results rather than a single fixed mileage number, so owners are better served going by sample condition than by calendar alone.
What electrical or sensor faults show up most on CX35-equipped trucks?
The transmission control module talks to the engine ECM and the rest of the truck over a CAN data link, and intermittent no-shift or no-start-lockout complaints often trace back to a chafed or corroded connector in that external harness rather than the TCM itself - wiggling or moving the harness bringing the shifter back to life is a classic tell of a marginal CAN wire. Low or degraded fluid can also throw a gear dropout that looks electrical but is really a hydraulic pressure problem. Because these transmissions run behind a range of chassis platforms, proper fault code reads generally need the factory diagnostic software rather than a generic code reader. Any no-start-lockout or intermittent shift fault tied to wiring should have your dealer verify the harness and TCM before parts are replaced.
What do the OL, OT, and LO warnings mean, and do they point to clutch pack or torque converter wear?
OL, OT, and LO on the shift pad correspond to over-limit, over-temperature, and low oil conditions, and they are the transmission protecting itself rather than random glitches. An over-temperature warning after sustained PTO work or grade pulling usually means the cooler circuit or fluid condition needs a look before assuming clutch damage. Persistent low-oil or over-limit codes paired with slip or a neutral feel in a specific gear point at clutch pack or solenoid wear in that circuit, since the electro-hydraulic clutches rely on precise pressure control to lock up cleanly. Repeat OT or OL codes under normal load should have your dealer verify cooler flow and clutch pack condition before the transmission is returned to service.
What causes a slip or neutral feel in one particular gear on these transmissions?
When a specific gear feels like it drops to neutral or slips under load, the pattern usually traces to that gear's clutch solenoid rather than a generalized transmission problem - loss of pressure at the solenoid test port for that clutch is the first thing techs check. Because the CX-series uses fully modulated electro-hydraulic clutches instead of simple mechanical bands, a single failed or sticking solenoid can take out one gear while the rest of the transmission shifts normally. Contaminated or low fluid makes the same symptom show up more broadly across gears instead of just one, so fluid condition is usually checked before condemning a solenoid or clutch pack.
What should a buyer check before purchasing a truck with a used or high-hour CX35 transmission?
Pull PTO hours alongside engine and travel hours through the truck's telematics if available, since PTO-heavy trucks load the transmission differently than highway-only units with the same odometer reading. Check fluid color and smell for burnt odor or metallic contamination, and ask for service records showing fluid and filter changes at or ahead of the sampling-based interval rather than a skipped schedule. Drive the truck through a full shift cycle under load, including the direct-drive gear, and watch for hesitation, slip, or a neutral feel in any one gear. Check the external harness at the TCM connector for chafing or an oil-swollen sheath, since that is a known source of intermittent shift and no-start-lockout complaints on these platforms. Have your dealer pull stored fault codes and review clutch pack pressure history before finalizing any purchase on a high-hour unit.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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