A/T - Torque Converter Clutch Shudder
84olds3
SUBJECT THM 125C TORQUE CONVERTER CLUTCH NUMBER: 84-T-16
SHUDDER DIAGNOSIS
DATE: Aug. 22, 1984
MODELS/YEARS 1982-84 CUTLASS CIERA, OMEGA & FIRENZA
SECTION: 7A
This bulletin summarizes and supersedes Dealer Technical Bulletins 82-T-19 and 83-T-16.
Some THM 125C 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 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":
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 tightening 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 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 no. 8643645 should be used on all models to prevent shudder. The service part does not have an orifice cup plug.
FIGURE 1 - AUXILIARY VALVE BODY (COVER SIDE):
X 4. There are two types of auxiliary valve bodies in service.
One has a orifice cup plug and the other does not. See Fig.
1. If the transaxle being serviced has the auxiliary valve body with the orifice cup plug, particles of the auxiliary valve body cover gasket may have torn loose. This material may be sticking the torque converter clutch apply valve and/or plugging the converter release orifice in the control valve body spacer plate. If this is found, disassemble the auxiliary valve body and thoroughly clean. Also, be sure to remove any gasket particles in the valve body spacer plate converter release orifice hole and replace the auxiliary valve body cover gasket, part no. 8653947.
X 5. Check the valves in the auxiliary valve body for freeness.
They must move in and out of their bore without sticking.
FIGURE 2 - THM 125/125-C TRANSMISSION I.D. NAMEPLATE YPSILANTI, MICHIGAN:
FIGURE 3 - THM 125/125-C TRANSMISSION I.D. NAMEPLATE WINDSOR, CANADA:
TCC APPLY TCC CROWD
SHUDDER SHUDDER
X 6. For gas engine/transaxles, the auxiliary valve body
converter clutch control regulator spring may be weak and require replacement with the new spring, part no. 8637888. The new spring has a stronger load, and went into production on February 20, 1984 for U.S. built and March 5, 1984 (Julian Date 065) for Canada built THM 125C transaxles. Refer to Chart 1 for serial number breakpoints. For explanations of nameplates, refer to Fig. 2 (U.S.) and Fig. 3 (Canada).
X X 7. Inspect the pump shaft-to-valve body seal for cuts, damage,
or distortion.
X X 8. A new governor pressure switch went into production
for diesel models only in late April 1982. This change corrects the "shudder" feel by raising the converter clutch apply speed. In servicing diesel model transaxles for this condition, refer to the following chart for proper model usage for 1982 models:
Governor Switch
Model Part Number
OP, HU, HY, H6, HR 8643369
HW 8637296
HS 8643368
CD,HI,HC 8643367
FIGURE 4:
FIGURE 5 - TURBINE SHAFT SEAL REPLACEMENT:
X 9. Inspect the turbine shaft Teflon (R) seal O-ring seal for
damage, cuts, or distortion. See Fig. 4 for these parts. If the Teflon (R) seals require replacement, make sure they are installed and sized as shown in Fig. 5.
FIGURE 6:
X 10. Inspect the turbine shaft seal grooves. A step in the bottom
corners of the seal groove will keep the seal from contacting the side wall of the groove and will prevent proper sealing. See Fig. 6. If this condition is found, replace the turbine shaft and seals.
FIGURE 7 - CASE COVER - VALVE BODY SIDE:
X 11. Check the case cover sleeve converter feed oil hole for
being out of alignment with the oil channel in the case cover. See Fig. 7. Inspect gasket pattern for leakage at converter apply passage. If gasket contact pattern is not complete, replace case cover.
X
12. Check the converter end play, using tool J-29830A. The
end play specification is .5 mm (.020"). Converters with end play more than .5 mm (.020") must be replaced.
X 13. The turbine shaft sleeve may be leaking excessively. If all
of the above items are OK, replace this shaft.
Model Serial No.
CA 2226
CB 156657
CE 67281
CF 5938
CT 4574
EB 2639
EF 6579
EI 5544
EJ 1006
EK 8843
EL 3594
EM 3062
EN 4984
EP 2085
Model Serial No.
EQ 11686
EW 1007
HC 1748
HM 2235
HP 1154
HS 11705
HX 4897
HY 20840
PD 2080
PE 50353
PF 22983
PG 47268
PJ 6007
PW 67271
Chart 1 - U.S. Models