Transmission Input Shaft Bearing

Replace the transmission input shaft bearing by removing the transmission from the vehicle, disassembling the front pump housing, and installing a new bearing assembly.

Warnings

Tools required

Parts

• Transmission input shaft bearing × 1 — Use OEM specification
• Front pump seal × 1 — Use OEM specification
• Transmission front pump gasket/O-ring × 1 — Use OEM specification
• Transmission pan gasket × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification
• Flywheel bolts (if torque-to-yield) × 6 — Use OEM specification
• Transmission filter (recommended) × 1 — Use OEM specification

Fluids

• Mercedes-Benz ATF 134 — 10 qt

Preparation

1. Ensure vehicle is on a level surface with adequate overhead clearance for engine support fixture
2. Disconnect negative battery terminal and wait 15 minutes for SRS system to discharge
3. Raise vehicle on lift to comfortable working height with full undercarriage access
4. Remove engine undertrays and transmission undertray panels
5. Install engine support fixture or overhead hoist with load leveler to support engine weight
6. Place transmission drain pan under transmission and drain fluid via drain plug
7. Allow transmission to drain completely (15-20 minutes minimum)
8. Disconnect exhaust system at manifolds and support/remove as needed for transmission clearance
9. Remove driveshaft and mark position relative to rear differential flange for reinstallation

Procedure

1. 1

   Disconnect transmission electrical and mechanical connections
   Disconnect transmission wiring harness connectors including conductor plate connector, shift solenoid connectors, and speed sensors. Label each connector for reinstallation. Disconnect transmission cooler lines at transmission (be prepared for residual fluid spillage). Remove dipstick tube if equipped. Disconnect shift linkage at transmission selector lever.
   Torque spec

   Sensor Bolts15 Nm (11 lb-ft)
2. 2

   Remove torque converter access cover and mark converter position
   Remove torque converter access cover from bellhousing. Rotate engine via crankshaft pulley bolt to access each torque converter-to-flywheel bolt. Mark torque converter position relative to flywheel with paint marker before removing bolts. Remove all six torque converter bolts and push converter back into transmission bell housing to disengage from flywheel.
   ⚠Ensure torque converter is fully pushed into transmission and secured before lowering transmission to prevent it from falling out during removal.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)

   Flywheel Bolts95 Nm (70 lb-ft)
3. 3

   Remove transmission crossmember and mounts
   Support transmission securely with transmission jack positioned at pan rail. Remove transmission crossmember mounting bolts from chassis. Remove transmission mount-to-transmission bolts. Carefully lower transmission jack slightly to access upper bellhousing bolts while maintaining support.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)
4. 4

   Remove transmission from vehicle
   Remove all bellhousing-to-engine bolts (typically 8-10 bolts of varying lengths - note positions). Verify all electrical connectors, cooler lines, and linkages are disconnected. Carefully slide transmission rearward to disengage input shaft from pilot bearing and clear engine dowel pins. Lower transmission on jack while maintaining level orientation. Guide transmission clear of engine bay and place on sturdy workbench.
   ⚠️Verify torque converter is retained in transmission during removal. Use a strap or retention tool to prevent converter from sliding out and causing injury.
5. 5

   Remove valve body and internal components access
   With transmission on workbench, remove transmission pan bolts in reverse criss-cross pattern. Remove pan and gasket. Remove transmission filter. Remove valve body mounting bolts (note different lengths and positions). Carefully lower valve body assembly and disconnect internal wiring connectors. Remove conductor plate if necessary for access.
   Torque spec

   Pan Bolts22 Nm (16 lb-ft)
6. 6

   Remove front pump assembly
   Remove torque converter (if not already removed). Remove front pump mounting bolts from transmission case. These bolts secure the pump housing to the case. Use slide hammer or carefully pry pump assembly straight out of case bore to avoid damage. Note pump depth/positioning for reinstallation. Remove pump gasket/O-ring from case.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)
7. 7

   Disassemble front pump and remove input shaft bearing
   With front pump assembly on workbench, remove pump cover bolts if applicable. Remove snap ring retaining input shaft bearing in pump housing. Using appropriate bearing puller or hydraulic press with proper supports, carefully press or pull input shaft bearing from pump housing bore. Inspect housing bore for scoring, wear, or damage. Clean housing thoroughly with solvent.
   ⚠Apply force only to inner bearing race when removing bearing to prevent damage to housing bore. Do not strike bearing with hammers.
8. 8

   Install new input shaft bearing
   Clean new bearing and verify it matches old bearing exactly. Measure and record bearing inside and outside diameters. Using hydraulic press or bearing installation driver, press new bearing squarely into pump housing bore until fully seated against stop or to original depth. Apply force only to outer bearing race during installation. Install bearing retaining snap ring ensuring it seats fully in groove. Verify bearing rotates smoothly without binding.
   ⚠Bearing must be installed perfectly square to housing bore. Cocked bearing installation will cause immediate transmission failure.
9. 9

   Measure bearing preload and end play
   Install input shaft into new bearing (without seals installed). Mount dial indicator to measure input shaft end play. Input shaft end play should be within Mercedes specification (typically 0.3-0.8mm). If out of specification, selective thrust washers may need replacement. Verify bearing rotates smoothly with no roughness or binding. Check bearing preload per manufacturer specifications.
   ℹ️Incorrect end play will cause bearing failure or clutch pack malfunction. Verify measurements carefully before proceeding.
10. 10

    Reassemble front pump assembly
    Install new front pump seal using appropriate seal installation tool. Lubricate seal lips with ATF. If pump has internal components that were disassembled, reassemble in reverse order ensuring all components are clean and properly oriented. Install new pump gasket or O-ring on pump housing. Lubricate all internal components with clean ATF 134 before final assembly.
    Torque spec

    Mounting Bolts37 Nm (27 lb-ft)
11. 11

    Install front pump assembly to transmission
    Verify transmission case pump bore is clean and undamaged. Align pump assembly with case ensuring gasket/O-ring is properly positioned. Carefully slide pump assembly straight into case bore to full depth. Install pump mounting bolts and tighten to specification in criss-cross pattern. Verify pump is fully seated and flush with case face.
    Torque spec

    Mounting Bolts37 Nm (27 lb-ft)
12. 12

    Reinstall valve body and transmission pan
    Reconnect conductor plate electrical connections if removed. Carefully raise valve body into position and connect internal wiring connectors. Install valve body mounting bolts to specification (note correct bolt positions). Install new transmission filter. Clean pan mating surface thoroughly. Install new pan gasket and transmission pan. Tighten pan bolts in criss-cross pattern to specification.
    Torque spec

    Pan Bolts22 Nm (16 lb-ft)
13. 13

    Reinstall transmission to vehicle
    Apply thin coat of high-temperature grease to torque converter hub. Verify torque converter is fully seated in front pump (should engage three times when pushed in - oil pump drive, stator support, then input shaft). Raise transmission into position ensuring torque converter remains retained. Align transmission with engine dowel pins and carefully slide forward onto engine. Install all bellhousing bolts to specification. Install transmission mounts and crossmember.
    ⚠️Verify torque converter is fully seated by measuring depth from bellhousing face to converter mounting surface. Should be minimum 15-20mm recessed.
    Torque spec

    Mounting Bolts37 Nm (27 lb-ft)
14. 14

    Complete transmission installation and fill fluid
    Align torque converter to flywheel using previous alignment marks. Rotate converter if needed. Install torque converter-to-flywheel bolts and tighten in star pattern to specification. Install torque converter access cover. Reconnect all transmission electrical connectors, cooler lines, and shift linkage. Install driveshaft to original position marks. Reconnect exhaust system. Install new drain plug crush washer and install drain plug. Fill transmission with approximately 5 quarts ATF 134 initially through fill tube.
    Torque spec

    Flywheel Bolts95 Nm (70 lb-ft)

    Cover Screws15 Nm (11 lb-ft)

    Transmission Drain Plug30 Nm (22 lb-ft)
15. 15

    Perform final checks and fluid level procedure
    Reconnect battery negative terminal. Start engine and verify no leaks at transmission pan, cooler lines, or pump seal. With engine at idle and transmission in Park, add additional ATF 134 to bring level to cold mark. Test drive vehicle through all gear ranges and re-check fluid level hot per Mercedes procedure (transmission at operating temperature 80°C, engine running, level ground). Top off as needed. Clear any stored transmission codes and perform transmission adaptation reset if available on scan tool.
    ℹ️722.9 transmission requires specific hot fill procedure with transmission at exact temperature. Overfilling or underfilling will cause shifting problems.

Reassembly

1. Torque all fasteners to exact specifications in proper sequence - particularly flywheel bolts and transmission pan bolts
2. Verify all electrical connectors are fully seated and locked
3. Use only genuine Mercedes-Benz ATF 134 fluid - substitute fluids will damage transmission
4. Install all undertray panels and ensure proper clearance with no interference
5. Road test vehicle verifying smooth shifts through all ranges before returning to customer

Verification

• Start engine and verify no fluid leaks at transmission pan, pump seal, cooler lines, or drain plug
• Verify transmission engages all forward and reverse gears smoothly without slipping or harsh shifts
• Road test vehicle and verify normal shift points and quality through full operating range
• Scan transmission control module for fault codes - there should be no transmission-related codes stored
• Verify transmission fluid level is correct at operating temperature using proper hot fill procedure
• Check for abnormal noise from transmission input shaft area during operation - should be smooth and quiet
• Monitor transmission temperature during test drive - should reach and maintain normal operating temperature (80-95°C)

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