OK so here's the deal, I completed my transmission build which included gearspeed carbon-coated syncros, new OEM third gear and 3/4 shift fork, and OBX lsd. I had a shop install the syncros and 3rd gear, then I reassembled the transmission myself. I know 110% that I put it together correctly (I have reassembled many transmissions with no issues).

Gears 1-4 and reverse work flawlessly. When I shift to 5th I can feel (and hear) the syncro sleeve slide over the syncro and the shifter stays in the 5th position, but the car acts as if its in neutral. It revs freely and DOES NOT grind when shifted to 5th. It seems like the syncro sleeve does not engage the dog teeth on the gear. I have taken the transmission back out and apart twice and inspected it. When I bench-shift it with the case off, the syncro sleeve engages the gear.

Any ideas at all? Thanks!