A/T - 700R4/4L60 Changes For 1988

SIL 89-8 (Mar)

SUBJECT: Hydra-matic 4L60/THM 700R4

Changes for 1988

VALVE BODY & SPACER PLATE







Valve body and spacer plates are changed to improve consistency for the 1-2 and 3-4 shifts. The valve body has revised 1-2 and 3-4 shift valve trains (See Figure 1). With the changes, the number 9 check ball has been eliminated (See Figure 2).

INPUT CLUTCH ASSEMBLY




This applies only to the YDM, YMM, YWM, and YZM models. These transmissions have 3-4 boost springs added to improve the release of the 3-4 clutch on downshifts (See Figure 3). 3-4 clutch boost springs should be installed on above models only. Part number for the 3-4 boost spring is 8667424. Five are required.

REVERSE INPUT CLUTCH PISTON




Reverse input clutch piston has a smaller bleed orifice (.095") on most models (See Figure 4). The MCM, MTM, PRM, TAM, TBM and YXM models continue using the previous piston with the .116" orifice.

The reverse input clutch piston with the .095" orifice is recommended as a replacement for all models that have the .116" orifice. Part number for the reverse input clutch piston with the .095" orifice is 8667841. EXCEPT FOR MODELS LISTED ABOVE.

CASE




The slot located in the case hub, at the lo/reverse piston, no longer extends through the hub. This was done to eliminate the possibility of a burr, on the inside edge of the slot, cutting the inner piston seal during assembly (See Figure 5).