Hi,
I have a 1986 Pontiac Firebird Transam 305 AT. The rear just went in it. I changed it and took it for a ride and it won't shift. Is this a coincidence or did I get the wrong rear for it? Does the gear shift ratio have anything to do with the trans not shifting? I'm at my wit's end here. Any help would be appreciated!
Thanks!

 

How about a question 1st?
What happen when you lost the rear?

 

It just started clanking in the rear as if the teeth were stripped out in the pumpkin.I pulled over and trailered it home.

 

Another stupid question, I am assuming it's an automatic and if so can you shift it manualy or will it not shift in drive?

 

Guessing here: Turbo 350's had a vacuum diaphram. Check vacuum hose at back of tranny?

 

If it won't shift out of 1st gear, but it will drive, then the vacuum modulator is likely malfunctioning. As gwampa said, check the vacuum line at both ends. If this is the case, it will also "free wheel" when you let off the gas. They don't often break, but they can.

If it won't shift into gear at all, check linkages etc that may have been moved or shifted during repair.

 

Had a 75 TA that ruptured the diaphram in the modulator and I sucked a couple of quarts of tranny fluid through the vacuum line. Doesn't happen often, but when stuff like this does it can be a real pain. If it is the diaphram, B&M makes a replacement that can be adjusted to control shifts. Let us know what it is.