A/T - AOD Reverse Drum Changes

TSB 86-21 (May)

Subject: FORD AOD

REVERSE DRUM CHANGES




The later Ford AOD transmissions use a thrust "bearing" between the reverse drum and the forward drum. The earlier units use a thrust "washer" as in the figure (marked A). The later drums, in most cases, will have one or more grooves cut into the outer face of the drive lugs (marked C).

These drums are interchangeable if the matching washer type is kept with the drum. The fact of the drum surface next to the washer (marked B) is cut down about .090" on the later drums to gain clearance for the thicker thrust "bearing". Otherwise the surface (B) will appear to be the same.

Caution:
The use of a late drum with the early 6-tanged thrust washer will result in excessive end clearance.

The use of an early drum with a late thrust bearing will result in a "locked" gear train.

The approximate distance from washer face "B" to the opposite face of the drum, where it rides against the pump (select) washer is:

2.290" on EARLY drums
2.200" on LATE drums