Allison Transmission Oil Leak, Abnormal Knocking Noise Heard at Idle (Diagnose and Repair as Required)

This bulletin is being revised to include new Warranty Labor Information. Please discard Corporate Bulletin Number 03-07-30-038 (Section 07 -- Transmission/Transaxle).

Some customers may comment on a transmission oil leak from the bottom of the converter housing, or a knocking type noise is heard with the engine running.

The flywheel to converter mounting bolts may have worked loose from engine/road vibration. Use the diagnosis procedure given in this bulletin to diagnose the vehicle for this potential cause.

If the under vehicle inspection reveals transmission oil is leaking from the bottom of the converter housing to inspection cover interface, perform the following diagnostic procedure.

For the diagnosis procedure, perform the steps indicated below.

1. Disconnect the negative battery cable.
2. Raise the vehicle.



3. Remove the positive battery cable nut and cable from the starter.
4. Remove the solenoid nut and wire from the starter.



5. Remove the starter motor bolts and reposition the starter.
6. Remove the flexplate inspection cover.



7. Remove the engine protection shield bolts and shield (skid plate), if equipped.




Important: Rotate the engine clockwise ONLY. Rotating the engine counterclockwise may loosen the crankshaft balancer bolt.

8. Rotate the crankshaft until a converter bolt is observed.
9. Place an observable mark on the flywheel next to the converter bolt observed in step 8.

Important: The following steps must be undertaken with extreme care and precision. Determining whether or not this bulletin applies will be determined in the following steps.

10. Set your torque wrench to measure 38 N·m (28 lb ft) of torque.
11. Set your torque wrench to LOOSEN bolts, counterclockwise direction.

Important: 

•	If in step 12 a bolt turns before the torque wrench clicks, the bolts are loose and this bulletin must be performed. Skip to the Correction statement below for details on replacing the flywheel, torque converter bolts and the transmission oil pump.

•	If in step 12 the torque wrench clicks before the bolt turns, THIS BULLETIN DOES NOT APPLY. Continue with step 13.

12. Carefully attempt to loosen the flywheel to converter bolts. ALL SIX BOLTS MUST BE CHECKED.
13. Reposition the observable mark at the 6 o'clock position.
14. Set your torque wrench to measure 40 N·m (30 lb ft) of torque.
15. Set your torque wrench to TIGHTEN bolts, clockwise direction.
16. Carefully recheck the six (6) flywheel to torque converter bolts for proper torque.
17. Continue the transmission oil leak diagnosis and repair following the repair procedures outlined in Service Information.

Important: After completing this modification, the transmission control module (TCM) shift adapts must be relearned for proper transmission operation. Follow the procedure outlined in Corporate Bulletin Number 02-07-30-032A to quickly relearn the transmission shift adapts.

Tools Required:

The following special tools will be required for the completion of the repair.

For transmission removal, refer to the proper Service Information Document ID #826485, skipping steps 1 through 5. These have been completed during the diagnosis procedure. After transmission removal, return to this document for additional instructions.

Caution: The Allison® 1000 Series (M74) transmission has a dry weight of approximately 150 kg (330 lbs). The torque converter has a dry weight of approximately 29 kg (63 lbs).

1. Install the J 42847 Flywheel Holding Tool to the engine starter mounting tabs.
2. Remove the engine flywheel bolts and remove the engine flywheel.

Important:  Make sure the flywheel is installed correctly. "Engine Side" is stamped on the flywheel to aid with installation.

3. Using NEW bolts, install a NEW flywheel.

Tighten the flywheel to crankshaft attaching bolts in a Star Pattern

•	Tighten all the bolts to 40 N·m (30 lb ft).

•	Tighten all the bolts a second pass to 80  N·m (59 lb ft).

•	Tighten the bolts a final pass to 100  N·m (74 lb ft).

4. Remove the J 42847, Flywheel Holding Tool.
5. Follow the Correction procedures of Corporate Bulletin Number 03-07-30-011 for additional repair information. This bulletin will provide instructions on the replacement of the oil pump cover and pump as well as the torque converter bleed down springs. Be sure to replace all of the parts listed in the parts list at the end of this bulletin.
6. For transmission installation procedures, refer to the proper Service Information Document ID #826485.

*Required only if the vehicle is a 4 wheel drive vehicle.

Important: 

For vehicles repaired under warranty, use: