Faststang- How many miles are on your T-5, 4th gear is a direct drive so I would think it just a worn out sycro but with out seeing it or taken it down.... It's seems strange that it's fourth, usually 2nd goes way before fourth does. Do any of the other gears grind at times. Looks like it's time for a rebuild. You should be able to get by with the 94pc set for D&D, $149.00.
90dpscoupe- If your cable is new it may have stretched, make sure the locking nut is tight at the bell housing I had one back off one time, I have no idea how it did that
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My Ride Check Out My Site 91GT, Holley SysteMAX II Kit-Heads 2.02" x 1.60",Full MAC exhaust 1-5/8" Long tubes, 2-1/2" O.R H-Pipe, 2 1/2" cat back, 12" K&N Filter, RNH PERFORMANCE Ram Air, Ron Davis Radiator, Full Suspension,3:73's, Welds, Best on new motor-12.60 @ 108, no traction 1.98