A/T - THM 440-T4 Erratic Shifts/No Upshifts
Number 87-7-40 Date 8/87Subject: ERRATIC SHIFTS/NO UPSHIFTS
1984-87 6000 AND BONNEVILLE MODELS EQUIPPED WITH THM 440-T4 (ME9)
BULLETIN COVERS:
Erratic shifts or no upshift in a THM 440-T4 transaxle may be caused by particles of hardened Imprex (TM) material lodging in the governor pressure channel.. (Imprex (TM) is an "impregnation plastic" used in the manufacturing of cases to help seal the case and minimize porosity.)
Figure 2 - Governor Assembly:
Figure 3 - Governor Oil Pipe And Accumulator Assembly:
SERVICE ACTION: (Figures 2 and 3)
1. Remove governor assembly (5) from transaxle and clean with solvent.
2. Inspect governor for binding weights and/or mispositioned springs. To verify operation, turn governor upside down and pour solvent into the governor shaft. Check for leakage past the checkballs. If leakage is noted, replace the governor assembly.
3. Reinstall governor cover (9) without the governor assembly.
4. Start the engine and move the selector lever to Drive (D) position. Allow the engine to run for 15-20 seconds.
5. Move the selector lever to Park (P) and stop the engine.
6. Reinstall the governor assembly (5) into the transaxle and road test the vehicle to verify transaxle operation.
If erratic shifts or a no upshift condition continues:
7. Remove and clean governor oil pipe retainer (129), orificed cup plug (127), governor feed and return pipes (125, 124) accumulator cover (121) and governor screen (126).
Figure 1 - THM 440-T4 Transaxle Identification Information:
SERVICE MANUAL REFERENCE:
Refer to the THM 440-T4 (ME9) Automatic Transaxle On-Car Service Section in the appropriate Service Manual for governor service information.