Car: 1996 Z28 M6; 90,000 miles; Stock with the exception of a BilletPlus Shifter

Problem: Recently (less than 5,000 miles ago) had the transmission rebuilt (Tick Performance, Mooresville, NC) due to the tranny failing to get into 1st Gear on the initial attempt. Once it was in 1st, however, it was in there to stay and the problem wasn't evident. That problem has gone away with the rebuild and I've got another issue that is showing up. There is significant vibration in 3rd and 5th particularly under any mid to high rpm. Also, when I let off the gas completely and let the gears slow the car, the shifter (when in 3rd and 5th) moves toward the rear of the car. Likewise, when I get back on the gas, the shifter moves forward again. Any clarification of what's going on here would be appreciated.

Thanks for your help!

 

Ive rebuilt quite a few T56's and this is new to me. 3rd and 5th arn't even in the same part of the tranny. 5-6 and reverse share the same shift fork rod actuating mechanism, but 3-4 and 1-2 are on a seperate one.

How is the rear tranny mount?