I have a ‘91 F150 with a 5 speed. I have had the trans in and out of this thing several times. However I am now chasing a clutch issue. I swapped out the trans for a new one along with a new clutch, pressure plate, throw out bearing, pilot and had the flywheel turned. After swapping this out, I noticed that everything was working great. The next day I drove it to work and all was good in the morning when I started out. Once the truck got to running temp the engagement of the clutch changed drastically. As the truck got hotter the clutch engagement got “bouncy”? Meaning from a start with a little throttle and as you start to bring the clutch in the truck would begin to lunge harder. Kind of it like you had really badly warped rotors and everything shakes like crazy. Then If you let it all cool down it would go back to having nice smooth engagement again and get more harsh as it warmed back up. I don’t think it is from riding the clutch at all just because I could use the clutch getting in the highway and it is fine when cold then not shift at all until I exit at that point the truck is hot and the clutch is acting up again. This is always a consistent issue. Any info would be greatly appreciated.

This is the 3rd trans in this truck since I’ve had it. 1st one the forks died and bound two gears together and broke a bunch of stuff inside. The clutch on the replacement trans exploded so out it came for a new clutch. All was good with that for almost 100k miles. I put forks in that trans 2 times during that time without pulling the trans. At the 267k mile mark I decided to replace that trans with a rebuilt one. I bought a brand new flywheel, slave cylinder, PP, CD, PB, TB. When it was all done the new flywheel was rubbing the back of the block/ scatter shield. So I dropped it again, turned the original FW and put it all back together again. And yes I thoroughly cleaned everything before assembly and the clutch hydraulic system was pressure bled. I used sealant on the FW bolts and I used studs to guide the trans back in so there was no clutch plate loading. So I still don’t get why it feels this way. As a side note, starting out in second gear doesn’t shake the truck nearly as bad.