A/T - Noise/Vibration With Converter Clutch Applied
90chevy15GMC NUMBER: 91-7A-04
GROUP: 7A Automatic Transmission
DATE: June, 1990
CORPORATE
NUMBER: 077114
SUBJECT: NOISE/VIBRATION WITORQUE CONVERTER CLUTCH APPLIED
MODELS: 1989-91 C,S,T TRUCKS AND G,L,M VANS W/4L60 (THM 700-R4) AND 4.3L ENGINE
BULLETIN COVERS:
Service and parts information for HYDRA-MATIC 4L60 (THM 700-R4) transmissions which may produce a noise or vibration with the torque converter clutch (TCC) applied. This may happen if the damper spring stops, located within the torque converter damper, bottom out against the damper plate. This condition may occur in the following HYDRA-MATIC 4L60 models that are used with 4.3L LB4 engines:
9FMM, 9MAM, 9MFM, 9MXM, 9THM, 9TLM
OCAM, OCBM, OMJM, OMNM, OSHM, OTLM, OWAM To eliminate this condition, a torque converter containing damper springs with a higher spring rate and improved torque capacity has been released for production and service.
DATE OF PRODUCTION CHANGE:
The following dates show which transmissions contain torque converters with damper springs that
- may bottom out against the spring stops.
DIAGNOSIS INFORMATION:
The following diagnosis information will help you determine if the vehicle has a vibration condition caused by the damper spring stops bottoming out in the torque converter.
- Gear Range:
Drive 4 (overdrive) with TCC engaged -Vehicle Speed:
Approximately 40-50 mph with TCC engaged
- then step into the throttle slightly
- Conditions:
1. Noise, vibration or rattle.
2 Low frequency noise that builds up until the floorboards rattle.
3. Low growl or driveline grumble. Road grades or trailer loads may cause the conditions to be more prominent or extended.
The conditions should disappear when the TCC is disengaged.
SERVICE PARTS INFORMATION:
Part Number Description
8678979 Converter Assembly
Package 298 mm (DE5F)
Parts are currently available through GMSPO.
SERVICE MANUAL REFERENCE:
Information on converter assembly removal and installation is covered in the Automatic Transmission Unit Repair section of the appropriate Service Manual.
WARRANTY INFORMATION For vehicles repaired under warranty use:
Labor Operation: K7020 See Labor Time Guide for appropriate labor time.