Cbower

I put another AOD in my stang this weekend, when the pan was off I noticed that a part was not in this trans as in my last. It is round and is held in by a snap ring..Is this possibly an accumulator and is it important to have this in it.. I don't know anything about trans internals. It does not look like it has ever had anything there and it seems to shift ok although it is sluggish and shifting to early in my opinion