[Tom Goldman]

I didn't mention in my response to your question which was also on the .90 tech forum, If you are using a TCI brake the removal of the casting wall is critical for proper release .
I have had a trans in the shop that did not have this done and it was slow , not to your extreme , but slow.
Also how does the trans engage and release reverse ? does it react normally ?
If reverse is abnormal so will be brake release.
JW brakes also require the use of their regulator spring and reverse /rear accumulator spring.
here's a shot of the divider that must be removed for the TCI brake.