Thanks to all! A couple of quick answer before proceeding:
- The clutch does completely disengage, as this has been verified through 2 different tests. Plus, if the issue were the clutch (according to Tremec) the grinding would happening in other gears or coming out of 5th to 4th
- I don't recall off hand which oil was used. The first time the tranny was installed (prior to issues), I used the fluid provided by MDL. The second time the tranny was installed, I used fluid sent straight from Tremec with the rebuilt tranny - they were both different brands, but I couldn't tell you what type
- MDL wanted to help; however, Tremec's policy is to have their warranty work completed by their technicians (or, at least that's what Tremec said)
- The T-5 is (from what I understand) not a bad transmission for a HiPo 289; however, it all depends on how the car is driven and if the engine has many power modifications. Tracking with this tranny is no bueno - it's better to step up to the TKO 5-speed from what I understand.
I just got off the phone with Tremec, and they are going to do a 1 for 1 swap. I asked what they thought was causing the problem, and they said it could be two items that, if out of tolerance, would take out the 5th gear synchro. Also, they confirmed that they changed the 5th gear synchro and 5th gear originally before sending the transmission back. Also, another person had the same issue with their T-5 (although the serial numbers were very far apart), and their components are being sent to Mexico for testing as well.
So, I'll drive it for now, double clutch it into 5th, and wait for the new tranny to come. The saga continues!