C 1500 Truck 2WD V6-262 4.3L (1989)
Torque Converter: Customer Interest
Driveline - Rattle/Vibration Under Load TCC Applied
GMC NUMBER:
90-7A-95
GROUP:
7A-AUTOMATIC TRANSMISSION
DATE:
SEPTEMBER, 1990
CORPORATE
NUMBER:
077123
SUBJECT:
DRIVELINE RATTLE/VIBRATION WITH ENGINE UNDER LOAD AND TCC ENGAGED
MODELS:
1989-90 K TRUCKS WITH 4L60 (700R4) AND 4.3L ENGINES
GMC TRUCK RECOMMENDS THAT A COPY OF THIS BULLETIN ALSO BE FILED UNDER SECTION 4A PROPELLER SHAFT.
BULLETIN COVERS Service and parts information for HYDRA-MATIC 4L60 (THM 700-R4) transmissions which may produce a driveline vibration
or rattle with the engine under load at approximately 40 mph and with the torque converter clutch (TCC) applied. This condition may occur in the
following HYDRA-MATIC 4L60 (THM 700-R4) models that are used with 4.3L LB4 engines: 9MRM, OKAM To reduce this condition, a torque
converter containing damper springs with a higher spring rate and torque capacity has been released for production and service.
DATE OF PRODUCTION CHANGE The following information shows the transmissions which are in vehicles that may exhibit this condition:
Model
Date of Production
9MRM All
OKAM All
DIAGNOSIS INFORMATION The following diagnosis information will help you determine if a vehicle has the driveline noise or rattle condition:
-
Gear Range: Drive 4 (overdrive) with TCC engaged
-
Vehicle Speed: Beginning at approximately 40 mph (or higher) with TCC engaged - then step into the throttle slightly.
Conditions:
1. Noise, vibration or rattle
2.
Low frequency noise that builds up until the truck bed rattles
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.
Brake can be lightly applied to disengage the TCC for testing.
SERVICE INFORMATION For vehicles repaired under warranty use:
Labor Operation:
T8145 (Do not use Labor Code K7020 as would normally be used for converter replacements).
Labor Time:
4.0 hrs.
Add (with skid plate):
.2 hr
NOTE:
Labor Operation is coded to base vehicle coverage in the warranty system.
SERVICE PARTS INFORMATION
Part Number
Description
8681952
Converter Asm. Pkg. 298 mm
(DEAF)
Parts are expected to be available on August 27, 1990. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP
orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on
400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be
cancelled as incorrectly ordered while the 400 control is in place.
SERVICE MANUAL REFERENCE Information on converter assembly removal and installation is covered in the Automatic Transmission Unit Repair
section of the appropriate Service Manual.
