Transmission issue?


New Member
Apr 16, 2019
1997 4.6 Mustang GT. 10 year overhaul/rebuild project. At the home stretch, tried to drive, and won’t shift into gear while running.

Everything in front of the firewall is brand new. The transmission is the original but worked great before pulling it. Trans sat for 10 years without fluid, but the openings were capped and covered to avoid dirt and debris from entering. New clutch, flywheel, and throwout bearing. I can shift through all the gears super smooth with the car off, but with it running it will not. The shifter just stops (before going into gear) as if it’s hitting its end point without any grinding sound etc. With all my force, I can’t push it. After removing the dust cover and watching as the clutch pedal is pressed to the floor, it responds as it’s supposed to and the cable is definitely pulling the clutch fork to its max point. A side note, if started while in gear, I can drive in the gear it started in, but I can’t remove it out of gear.

My thought process is that maybe it needs to be “loosened up” a bit after sitting for so long? In lieu of this, I decided to start it in first, drive forward. Shut off, start up in reverse, back up. Repeat process. After doing this a couple of times, I seemed to have made very small improvements as noted below:

When starting in neutral and trying to shift into first gear, rather than a hitting a brick wall, I got grinding as if I tried to shift without the clutch. The second improvement was that while starting in gear, I was now able to remove the shifter out of gear and into neutral while running (couldn’t do that before with any amount of force).

Do you think that by continuing this process it will kind of loosen things up because the trans hasn’t moved in 10 years? Or don’t you think there is some other underlying issue? Really dumbfounded here and not looking to drop the trans again if that’s not the issue lol (longtube headers meaning lift engine, drop K-member, remove headers, disconnect trans). I’ve spent days searching through forums only finding the same results and am looking for a different approach to problem solving if anybody has ideas. Thanks!
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