K 3500 Truck 4WD V8-6.6L DSL Turbo VIN 1 (2001)
Torque Converter: Customer Interest
A/T - Allison 1000, Fluid Leak from Pump Area
Bulletin No.: 03-07-30-057
Date: November 10, 2003
TECHNICAL
Subject:
Transmission Fluid Leak From Front of Transmission - Torque Converter Housing/Pump Area (Remove 2 Lower Torque Converter Housing Bolts, Add
Copper Washers Under Bolts)
Models:
2001-2004 Chevrolet Silverado 2500/3500 Series Models
2001-2004 GMC Sierra 2500/3500 Series Models
with Allison(R) Series 1000 Automatic Transmission (RPO M74)
Condition
Some customers may comment on transmission fluid leaking from the front of the transmission. Diagnosis will indicate that the leak is coming from the
torque converter housing and pump area.
Cause
Two possible leak points in the pump area may be the two lower converter housing to main housing bolts. There have been case porosity issues that can
lead to fluid contacting the bolt threads and leaking out under the bolt head. Typically, porosity related leaks would begin at low mileage.
Correction
Remove the two lower torque converter housing bolts. Use the procedure listed below. If the bolt threads are wet with automatic transmission fluid
(ATF) when removed, it is likely that the porosity condition exists. A copper washer, P/N 10139097, can be placed under each of the bolt heads to
prevent future fluid leaks.
These washers were added to production transmissions beginning the week of September 8, 2003. If a transmission is being disassembled for service and
copper washers are found under these bolt heads, it is important that they be reinstalled during assembly.
If the bolt threads are not wet with ATF when removed, the cause of the leak may be due to any of the ten converter housing oil pump retaining bolts
being under-torqued or a damaged bolt seal. Refer to the Torque Converter Housing Bolt Seal Replacement procedure.
Important:
DO NOT replace the torque converter unless the following conditions exist:
^
The torque converter hub shows signs of damage.
^
The torque converter to flywheel bolts were loose.
Note:
The transmission must be in a vertical position (torque converter pointing up) whenever the torque converter is removed or installed. Removal or
installation of the torque converter when the transmission is in a horizontal position is likely to cause a cut or damaged oil pump seal assembly,
resulting in a leak.
1.
Remove the torque converter from the transmission. Refer to the Torque Converter Replacement procedure in the Automatic Transmission -
Allison sub-section of the Service Manual.
