A/T - Allison 1000, Leaks/Knocking Noise at Idle
Bulletin No.: 03-07-30-037CDate: October 18, 2005
TECHNICAL
Subject:
Allison Transmission Oil Leak, Abnormal Knocking Noise Heard at Idle (Diagnose and Repair as Required)
Models:
2001-2003 Chevrolet Silverado 2500/3500 Series Pickup Models
2001-2003 GMC Sierra 2500/3500 Series Pickup Models
with Duramax(R) Diesel (RPO LB7) and Allison(R) 1000 Series Automatic Transmission (RPO M74)
Supercede:
This bulletin is being revised to update Warranty Labor Time Information. Please discard Corporate Bulletin Number 03-07-30-037B (Section 07 - Transmission/Transaxle).
Condition
Some customers may comment that an abnormal knock noise is heard when the engine is running, or that there is an oil leak from the bottom of the converter housing.
Possible Cause
The Plate, A/transmission Flex (Flexplate adapter plate) to converter mounting bolts may have loosened from engine/road vibration. Use the diagnostic procedure given in this bulletin to diagnose the vehicle for this potential cause.
Technician Diagnosis procedure
If the under vehicle inspection reveals transmission oil leaking from the bottom of the converter housing to engine joint, perform the following diagnostic procedure.
For the diagnosis procedure, perform the steps indicated below.
1. Disconnect both of the negative battery cables.
2. Remove the transmission fluid level indicator.
3. Raise the vehicle until the right front wheel and tire can be removed.
4. Remove the right front wheel and tire.
5. Remove the right front wheel house inner panel retainers (2).
6. Disconnect any harness retainers attached to the inner panel.
7. Remove the inner panel (2).
8. Remove the positive battery cable nut and cable from the starter.
9. Remove the solenoid nut and wire from the starter.
10. Remove the starter motor bolts and reposition the starter.
11. Remove the engine protection shield bolts and shield (skid plate).
Important:
Rotate the engine clockwise ONLY. Rotating the engine counterclockwise may loosen the crankshaft balancer bolt.
12. Rotate the crankshaft until a converter bolt is positioned in the starter opening.
13. Place an observable mark on the crankshaft pulley at the 6 o'clock position.
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.
14. Set your torque wrench to measure 58 N.m (43 lb ft) of torque.
15. Set your torque wrench to LOOSEN bolts, the counter clockwise direction.
Important:
^ If in step 16 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 flexplate, torque converter bolts and the transmission pump.
^ If in step 16 the torque wrench clicks before the bolt turns, THIS BULLETIN DOES NOT APPLY. Continue with step 17.
16. Carefully attempt to loosen the flexplate adapter plate to converter bolts. ALL SIX BOLTS MUST BE CHECKED. The previously placed observable mark will be in the 4 o'clock position when all bolts have been checked.
17. Reposition the observable mark on the crankshaft pulley to the 6 o'clock position.
18. Set your torque wrench to measure 60 N.m (44 lb ft) of torque.
19. Set your torque wrench to TIGHTEN bolts, clockwise direction.
20. Carefully recheck the six (6) adapter plate to torque converter bolts for proper torque. The observable mark will be in the 4 o'clock position when all bolts have been checked for proper torque.
21. Continue the transmission oil leak diagnosis and repair following the repair procedures outlined in Service Information.
Correction
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 special tools shown will be required for the completion of the repair.
After transmission removal, return to this document for additional instructions.
Caution:
The Allison(R) 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).
^ Use caution when removing, installing, servicing or moving the transmission in order to prevent personal injury.
^ Get assistance when lifting the transmission. A hoist is the preferred lifting device. Ensure that the lifting device is adequate to support the transmission.
1. Remove the "Flywheel", "Plate, A/Transmission Flex". (Torque Converter Adapter) and "Retainer" from the engine crankshaft. Discard all eight of the flywheel to crankshaft bolts.
2. Using NEW bolts, install the "Flywheel", NEW "Plate, A/Transmission Flex". (Torque Converter Adapter) and "Retainer" to the engine crankshaft.
3. Tighten the attaching bolts in the pattern shown:
Tighten
^ Tighten the bolts to 79 N.m (58 lb ft).
^ Tighten the bolts an additional 60 degrees.
^ Tighten the bolts an additional 60 degrees a second time.
4. Follow the Correction procedures of Corporate Bulletin Number 03-07-30-011C for transmission repair information. This bulletin will provide instructions on the replacement of the oil pump and pump wear plate as well as the torque converter relief and lube regulator springs. Be sure to replace all of the parts listed. Refer to the Parts Information below.
Parts Information
Warranty Information
Disclaimer