A/T - 440T4 Harsh 3-2 Downshift

TSB: 88-44 (Oct)

SUBJECT: THM 440-T4

PROBLEM:
Harsh 3-2 downshift on 1985-1/2, '86, and 87 models

POSSIBLE SOLUTION: Trim 3-2 control valve spring

Part numbers are available from GM on replacement springs for the 3-2 control valve spring. The replacement spring will be approximately 1 lb. lighter than the existing spring in the valve body.

When rebuilding the 440-T4, it is recommended to trim the existing 3-2 control valve spring by two coils, or replace it with a factory replacement spring.




Always check the 3-2 control valve line-up before trimming the spring. The 1985 1/2, '86 and '87 models use the line-up shown in Figure 1. If a harsh 3-2 downshift is experienced on an earlier transmission, refer to SIL 87-5.