A/T - Fluid Leak Near Front Pump (Bushing Walkout)
89chevy13GMC NUMBER: 88-T-199
GROUP: 7A - Automatic Transmission
DATE: March, 1989
CORPORATE
NUMBER: 877143R
SUBJECT: PUMP FLUID LEAK CAUSED BY FRONT PUMP BUSHING WALKOUT FORCING FLUID PAST PUMP SEAL
MODELS: 1978-1988 C,K,P,R AND V TRUCKS, G VANS EQUIPPED WITH THM 400/475 AUTOMATIC TRANSMISSIONS
Figure No. 1:
Figure No. 2:
Some THM 400/475 models may experience a fluid leak coming from the converter or oil pump area. This could be caused by the front pump bushing walking forward, resulting in fluid being forced past the pump oil seal. A new bushing was introduced that has an increased hardness specification which results in a higher push-out load.
DATE OF PRODUCTION CHANGE: (Figure No. 1)
Beginning August 1, 1988 (Julian Date 213) all 1989 THM 400/475 transmissions were built with the new pump bushing.
IMPORTANT: When replacing the pump bushing
(003) it is required that the pump seal (002) also be changed at this time. (Figure No. 2)
SERVICE PARTS INFORMATION
Part No. Description
8623940 THM 400/475 Bushing-Pump Body
8670283 Helixseal Assembly-Oil (optional
with 8670284)
Parts are currently available from GMSPO.
SERVICE MANUAL REFERENCE:
Refer to the Unit Repair section of the appropriate Service Manual for the proper pump bushing and seal replacement procedures.