A/T - Summary of Shudder Diagnosis
Number: 86-155Section: 7A
Date: Sept. 1986
Subject: THM 440-T4 SUMMARY OF SHUDDER DIAGNOSIS
MODEL AND YEAR: 1984-1986 ALL MODELS WITH THM 440-T4 TRANSMISSIONS
TO: ALL CHEVROLET DEALERS
This bulletin provides additional diagnosis information, and a new Part Number, cancelling and superceding Chevrolet Dealer Service Bulletin 86-41 (Section 7A) dated March 1986 which should be destroyed. This bulletin also supplements Chevrolet Dealer service Bulletin 85-34 (Section 7A) dated February, 1985.
A vehicle equipped with a 1984 through 1986 THM 440-T4 transaxle may experience a shudder condition which could be described as similar to driving over rough pavement. This condition may be the result of various engine and/or transaxle-related causes.
Before diagnosing for a transaxle-related shudder condition, make sure the condition is not engine-related.
Refer to the chart for trouble shooting procedures.
When performing any service procedure, refer to the appropriate service manual.
CONDITION INSPECT COMPONENT
FOR CAUSE
ENGINE-RELATED SHUDDER, Engine Fuel Delivery System Restriction or imbalance. For example,
OR "CHUGGLE" fouled fuel injectors due to deposits.
Engine Ignition System Improper operation. Includes items such
as fouled or broken spark plugs.
TCC APPLY SHUDDER Torque Converter Cover Dimpling caused by too-long bolts (Max.
length 15 mm).
Torque Converter See NOTE, following chart.
TCC APPLY SHUDDER OR Turbine Shaft Seals Missing or damaged.
CROWD SHUDDER (Crowd
shudder occurs after TCC apply, TCC Accumulator Piston Seal Cut or rolled. Refer to Bulletin HM 85-17
when accelerator is depressed) TCC Solenoid O-Ring Cut or broken.
Valve Body Gasket Torn or mispositioned.
TCC CROWD SHUDDER Downshift Delay Module Improper operation.
(Canadian 2.8 LE2 Only)
1-2 SHIFT SHUDDER 2nd Clutch Plates Replace steel and fiber plates (soak in
transaxle fluid for 30 mins. prior to
installation).
2-3 SHIFT SHUDDER Servo Release Pipe Seals Cut seals. Refer to Bulletin HM86-07.
SHUDDER UNDER LOAD OR Right Rear Engine Mount Engine grounding out.
ACCELERATION (1986 3.8L H-Body Only)
NO TCC APPLY, DELAYED TCC TCC Solenoid Apply Valve, Sticking in valve body. (At start of pro-
RELEASE, OR TCC APPLY AND/ TCC Pressure Regulator Valve duction 1986, the TCC regulator valve
OR RELEASE SHUDDER Or Spring spring was eliminated on the following
models: AAH, ACH, ADH, AFH, AMH, ARH, BHH, CFH, CHH, CMH, CNH, HBH, and HJH.)
SHUDDER IN REVERSE Right Rear Engine Mount Engine grounding out.
(1986 E-Body)
FIGURE 1 - TRANSAXLE IDENTIFICATION:
A 1986 THM 440-T4 transaxle built before March 10, 1986
(Julian Date 069) may exhibit a torque converter clutch apply shudder at 45-55 mph.
Refer to Figure 1 for transaxle identification.
The shudder condition may be caused by the damper plate not fully seating.
If the TCC apply shudder condition is exhibited, and all diagnostic procedures have been performed, replace the torque converter with a service converter as indicated
below.
MODEL TORQUE CONVERTER PART NUMBER
4CW, 5CM, 5CN, 5CP, 8656920
5CW, 5HA, 5HJ, 5HT, 6CFH, 6CMH, 6CNH