A/T - 3rd To 2nd Gear Downshift Bump

85-139
7A

OCT., 1985
Subject: 3-2 DOWNSHIFT BUMP
Model and Year: 1984-85 THM 440-T4 TRANSAXLES
MODELS CP-1985 & CM-1985-1/2
TO: ALL CHEVROLET DEALERS

Figure 1 - THM 440-T4 TRANSAXLE I.D. INFORMATION:

Some 1985 THM 440-T4 "CM" & "CP" model transaxles (refer to figure 1), may exhibit a 3-2 downshift bump. This condition may be most prevalent during a part-throttle downshift with the air conditioner operating. A slight transaxle tie-up condition which shakes or rattles the instrument panel during the downshift may also be experienced.
When servicing any 1985 THM 440-T4 "CM" & "CP" model for a 3-2 downshift bump, order and install service package part number 8646951.

Service package part number 8646951 contains one each of the following:

3-2 Control Valve Spring 1-2 Servo Boost Valve Instruction Sheet

Figure 2 - CONTROL VALVE ASSEMBLY:

Refer to Figure 2 of this bulletin and the appropriate Service Information Manual for proper installation procedures. Models "CP" are 1985 models while "CM" is a 1985-1/2 model. There are differences between the 1985 and 1985-1/2 models which are explained in Chevrolet Dealer Service Bulletin 85-86, published May, 1985.