My 75 coup has been jumping out of 2nd gear when decelerating since I got the car 3 years ago, so I pulled the engine/transmission last fall to fix it.
After disassembling the Borg Warner Super T-10, I could not see anything amiss so I installed new bearings and synchros and put it all back together again.
It still jumped out of 2nd gear, so I pulled the engine/transmission again and took the transmission to a transmission shop for them to go through it. After puzzling over it for a week, he asked another shop to take a look at it and they finally realized that the sleeve under the 1/2 gear set was not pressed on all the way.
While the engine was out this time, I decided to replace the camshaft. It was starting to wear and I wanted a bit more power (who doesn't!). After getting it all back together again, I drove it about 10 miles and the camshaft destroyed itself. I've build many engines over the years but never had an issue like this.
Since the engine was now full of metal from the camshaft and lifters, I took it to a machine shop to be tank cleaned and checked out. I showed them the camshaft, and the first question asked was "Did you add zinc additive to the oil?" Since 1980 this and other additives were removed from the oil because of the catalytic converters. I did not know this and there were no instructions with the camshaft.
The machine shop found that the crankshaft needed to be turned and the cylinders needed to be bored. So I put flat-top pistons in to gain a little compression (I get about 180 PSI and it should be about 10:1 compression ratio). I also got a Comp Cams camshaft which came with about 10 pages of instructions on oil/additive to use and break-in procedure.
After putting the engine back in for the 3rd time and starting it, it made an awful racket. It sounded like valve-train, but I could not pin it down. So back came the engine again (this time I left the transmission in place, thinking it would save some time). I took the heads to the machine shop and they found the valve springs were very weak. So they replace these and used the new style valve seals.
Back in whet the engine for the 4th time, but we could not get it to line up with the 4-speed transmission in place, so we pulled the transmission and put the engine/transmission in together.
It now runs great, and sounds a lot more powerful -- which is what I was really looking for in the new camshaft.
So a simple rebuild of the transmission turned into a complete overhaul of the engine. And guess what -- the transmission still jumps out of 2nd gear!
______________