Q45 No Reverse when Warm

[Blowinonstress]

So I recently got a 96 Q45t.The reverse seems to work perfectly fine when the vehicle is cold. Now after a while when the car warms it up it won't go into reverse.

I went ahead and put the transmission I had from my 94 Q45 which was rebuilt and worked fine before my engine blew. I put it into the 96 and, same issue only reverse when cold. So it the question is what could it be?

[Blowinonstress]

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