A/T - 440T4 Delayed Forward Engagement/Slips
SIL: 86-9 MaySUBJECT: 440-T4
PROBLEM: DELAYED FORWARD ENGAGEMENT, SLIPS ON TAKEOFF, AND/OR 2-3 UPSHIFT BUMP OR SHUDDER
A 1985 or 1986 THM 440-T transaxle (refer to figures) may exhibit delayed forward engagement, slipping on takeoff from stops, and/or a 2-3 upshift bump or shudder. The condition(s) may be caused by leakage in the 1-2 servo circuit, which controls apply and release of the 1-2 band.
Seals are included at both ends of the apply and release pipes (refer to figures) and on the servo piston. A damaged seal in any position may affect operation of the servo. A leaking apply pipe circuit may cause delayed forward engagement and slipping on takeoff when in first or second gear. A leak in the release pipe circuit may cause a 2-3 upshift bump or shudder. A 1-2 servo piston leak may cause any/all of the condition(s).
When performing transaxle service, check transmission fluid for burned condition (burned fluid loses its red color and has an acrid odor). Burned fluid may indicate major internal repair requirements.
If fluid condition is proper, inspect the servo pipe seals at both ends of each pipe and the 1-2 servo piston seals. The original pipes can be reused in the field service. Replace any damaged seal as outlined in the appropriate Service Manual. Refer to the following list for service part numbers.
PART NUMBER: DESCRIPTION:
8656567 Seal, 1-2 Servo Pipe to Valve Body
8656568 Seal, 1-2 Servo Pipe to Case
8658160 Ring, Oil Seal, 1-2 Piston
IMPORTANT
When installing the servo pipes into the control valve assembly, it is critical that the pipes are correctly aligned with the assembly bore to ensure that seal damage does no occur.
Note
On November 1, 1985 (Julian date 305) a revised production installation process for the 1-2 servo apply and release pipes/seals began, to prevent cutting the seals during assembly.