Century V6-260 4.3L DSL (1984)
Vehicle Speed Sensor: All Technical Service Bulletins
A/T - Torque Converter Clutch Shudder
Bulletin 84-7125-7
Date
Sept. '84
Ref. No. 84-285-7125
SUBJECT:
THM 125-C TORQUE CONVERTER CLUTCH SHUDDER DIAGNOSIS (SUMMARIZES AND SUPERSEDES BULLETINS
82-I-227A, GRP 70, #68; 83-126, GRP 70, #14 AND 83-32A, GRP 70, #1A)
MODELS AFFECTED: ALL THM 125-C TRANSAXLES
Some THM 125-C transaxles may exhibit torque converter clutch (TCC) shudder as the TCC applies and/or after it applies when the accelerator pedal is
depressed slowly (Crowd Shudder). These types of shudder are best described as a jerking sensation. In some cases the shudder may cause the instrument
panel to vibrate.
Listed below are items which may cause a "TCC Apply Shudder" and/or a "TCC Crowd Shudder".
CONDITION
CAUSE AND CORRECTION
Note:
Before any attempt is made to correct a TCC Shudder comment spark plug insulators should be checked for possible cracks. A cracked insulator
can cause a condition that may be misdiagnosed as TCC Shudder. Also a cracked insulator may not show up at idle or on a scope test.
TCC APPLY
TCC CROWD
SHUDDER
SHUDDER
X
X
1. An intermittent or incorrect signal from
the vehicle speed sensor (VSS). Dirt or grease on the reflective bar in the VSS may be sending an
incorrect or erratic signal so that the converter clutch engages early. An easy means of verifying this is
to check mph on an ALDL tool with that m the speedometer in the car - if the readings vary greatly,
remove the VSS and clean it.
X
X
2. The auxiliary valve body cover attaching
bolts may be loose or the bolt threads/holes may be shallow. If the holes are shallow, the bolts
will bottom out without torquing the cover down.
CONDITION
CAUSE AND CORRECTION
TCC APPLY
TCC CROWD
SHUDDER
SHUDDER
X
3. Some 1982 models were built with either an
exhaust hole or an orifice cup plug in the auxiliary valve body cover. The auxiliary valve body cover was changed to a solid cover (no exhaust hole or
orifice cup plug) in 1982. The service auxiliary valve body cover, part number 8643645, should be used on all models to prevent shudder. The service
part does not have, an orifice cup plug.