Harsh Upshifts - High Altitude Only

VI. HARSH UPSHIFTS - HIGH ALTITUDE ONLY

- 1985-86 Century models with 2.8L engines

Service Procedure:

Harsh upshifts for ALL GEARS at high altitudes may be caused by high line pressure due to low engine vacuum. This condition may be corrected on certain transaxle models by installing the appropriate aneroid modulator Service Package.


Service Parts Information:
Service Package Transaxle Model Identification
Number

8646956 6CFH, 6CMH, 6HBH, 6HJH
5CM, 5CN, 5CP, 5CW, 5HA, 5HJ, 5HT

8646966 6AAH, 6ACH, 6AFH, 6AMH
5AF, 5AM

8646967 6ADH, 6ARH

Parts are currently available from GMSPO.

Service Notes:

A new vacuum line from the engine to the vacuum modulator MUST also be installed when using the service packages listed above.

Part Number Vehicle Application

14062624 Century

Parts are currently available from GMSPO.

Other items affecting harsh upshift conditions are:
- engine vacuum leaks
- sticking modulator valve
- restrictions in the vacuum lines such as paint in the modulator tube and/or carbon at the throttle body fitting





Transaxle Identification Information