1994 Bonneville SSEi, new transmission about 3 months ago. Then things started going wrong. First, the car would drive for a mile or so then lose all gears, i.e., the engine would rev but the car wouldn't move. First time, the trans rebuilder said it was the PRNDL switch (neutral safety switch, which was throwing a code).
When that didn't fix it, he said the it was the torque convertor and replaced it under warranty. He also replaced the radiator (not under warranty) and said that the built-in factory trans cooler was leaking and damaged the transmission. OK, so it had over 160,000 miles on the radiator so it probably needed replacement anyway. It has run cooler since then, so I accepted that.
Then the car stopped engaging the transmission when you first started it. You had to let it idle for a couple of minutes before it would go. After that it would go just fine, shifted good, etc., but if it sat for more than an hour it would do it again. But at least once it got going it kept going... The transmission rebuilder determined that there was a vacuum leak. A free fix of what he said was the leak seemed to fix the problem.
Now the first problem has returned.. sorta. Symptoms: When first starting the car, it engaged the trans just fine and away you went, shifting normally. Suddenly it would lose transmission engagement, i.e., the engine would rev freely and you don't continue to move forward. After drifting to a halt, if you put the car in park, kill the engine, then restart (I mean you can restart immediately, or wait a few minutes. There doesn't seem to be a cooldown requirement), the trans re-engaged--no slippage--and off you go again. To a repeat performance. I drove the car 7 miles that way last night after my son called me at 11:30 to report he was stalled on the side of the road... The transmission engaged fine, then it didn't. Stop, park, kill, start, go. Worked all the way home.
Next morning: Started the car, put it in gear. Nothing. Not the slightest engagement forward or reverse. AAAAAARRRRGGGGHHH!
Oh, yeah--one more thing. If you turn the engine off in neutral and try to restart, it will not start. That'* odd. Used to start in neutral.
What can be going on here?

Keith

The new transmission, was it new new, rebuilt, or used but new to the car? There were some slight changes to the transmissions through the years 92-95.

Can you start the car fine, just can't get it to go in gear? Any gear? Can you put it into 1 or 2 and get a gear?

Lastly, where are you located? Might have a member near that can help diagnose it.

The trans is the original trans rebuilt. Car starts and and the engein runs fine, just stopped going into any gear at any time. I even tried with performance shift on and off, and traction control on and off. No engaging of the transmission, not even a little bit. I have no idea how I managed to get it home last night at midnight... Now I've had it hauled back to the transmission shop since it'* still under warranty. I didn't want to, even with the warranty, because they've been unable to figure out what was wrong and tend to blame things that "aren't covered under the warranty," so it costs me more money. I've put more money into the car than it'* worth already....
In any case, I'm located in Lebanon, Missouri... which is a long way from population centers like Kansas City and St Louis.
Keith

Are you absolutely sure the transmission fluid level is correct. It could cause all these sorts of problems if low.