Celebrity L4-151 2.5L (1982)
Vehicle Speed Sensor: All Technical Service Bulletins
A/T - THM 125C Torque Converter Clutch Shudder
Number:
84-171
Section:
7A (VIIc)
Date:
July, 1984
Subject:
THM 125C TORQUE CONVERTER CLUTCH SHUDDER DIAGNOSIS SUPERSEDES CHEVROLET BULLETINS 82-T-125,
83-T-41, AND 83-T-53
Model and Year:
ALL THM 125C
TO:
ALL CHEVROLET DEALERS
Some THM 125C transmissions 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 shudders 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
TCC Apply
TCC Crowd
Shudder
Shudder
X
X
1. An intermittent incorrect signal
from the vehicle speed sensor (V.S.S.). Dirt or grease on the reflective bar in the V.S.S. may
be sending an incorrect or erratic signal so that the converter clutch engages early. Remove
the V.S.S. 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.
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
Condition
Cause and Correction
TCC Apply
TCC Crowd
Shudder
Shudder
valve body cover was changed to a solid cover (no exhaust hole or orifice cup plug) in 1982. The service
auxiliary valve body cover, P/N 8643645, should be used on all models to prevent shudder. The service part
does not have an orifice cup plug (see Chevrolet Bulletin 83-T-41).