Harsh 3-2 Coastdown Bump At 15-22 MPH

V. HARSH 3-2 COASTDOWN BUMP AT 15-22 MPH

- 1985-87 Century, Electra/Park Avenue, Riviera and LeSabre models with transaxles built prior to December 18, 1986 (Julian Date 352) and 3.8L engines

Service Procedure:

A coastdown bump is obtained by allowing the vehicle to coastdown to 15-22 mph (with closed or zero throttle) and a sudden and forceful apply of the 1-2 band is felt when the transaxle shifts from third to second gear.

A harsh 3-2 coastdown bump may be caused by the 1-2 servo cushion spring. This condition may be corrected by replacing the 1-2 servo cushion spring with the part listed below. Refer to the chart below to determine the transaxle model and Julian Date when the new springs were first used in production units.

Transaxle Build Date/ Transaxle Build Date/
Model Julian Date Model Julian Date

7FBH 12-11-86/345 7FSH 12-11-86/345
7FCH 12-11-86/345 7FTH 12-11-86/345
7FJH 12-15-86/349 7FZH 12-12-86/346
7FKH 12-11-86/345 7HAH 12-15-86/349
7FNH 12-11-86/345 7HCH 12-18-86/352
7FRH 12-17-86/351

Service Parts Information:
Part Number Description
8668123 1-2 Servo Cushion Spring (559)

Figure 7

Parts are currently available from GMSPO.

Service Notes:

If the above condition persists make sure the 3-2 coastdown valve (located in the oil pump body) is not stuck and moves freely in its bore.