A/T - 440T4 Soft/Slipping 1-2 Upshift Flare

TSB 89-5 (Feb)

SUBJECT: HYDRA-MATIC 4T60/THM 440-T4

PROBLEM:
Soft, slipping 1-2 Upshift Flare, or no 1-2 Upshift

(When experiencing soft upshifts of any kind, always refer to ATRA TSB 88-18.)

CAUSE:
A 1-2 upshift flare, or no 1-2 upshift can occur if the two metal sealing rings bind in the grooves of the driven sprocket support. This will allow the sealing rings to wear into the 2nd clutch housing.

Inspect the metal sealing rings for wear (shiny appearance on outside diameter). Also inspect the 2nd clutch housing for wear at the location the sealing rings ride. If both inspections show no wear, the sealing rings have not been binding. If either inspection shows wear, replacement of the driven sprocket support is recommended.

CURE:
When replacing the driven sprocket support on any model, it is recommended to install a driven sprocket support that uses Vespel (TM) sealing rings. this is the updated 1987-up design driven sprocket support which retrofits all models.

PART NUMBER DESCRIPTION

8662523 Driven sprocket support with 4-lobe seals and Vespel (TM) sealing rings.




If the metal sealing rings show no wear, and the 2nd clutch housing shows no wear, the driven sprocket support is good. Many technicians condemn the support because it doesn't air check as well as the Vespel (TM) ring design. the driven sprocket support with metal sealing rings must meet four requirements:

1. Metal rings need fluid pressure, not air pressure, to push to to one side of the groove.

2. .004" maximum side clearance between metal ring and the ring groove.

3. Spinning action (Free movement in the grooves)

4. An unglazed bore to prevent them from spinning in the bore.