I have a firebird with a turbo 400 in it. I have torn into everything in the car except the transmission. I don't know a thing about them. It is leaking around the "range selector shaft" is the technical term for it. The shaft the shifter cable connects to. I was wondering how much of a job it is to replace the seal. Is it just an O ring that can replaced without tearing into the transmission? Any info would be helpful.

I did not do mine myself ,plus mine is a th350, but yes thete are O rings there, they didnt charge me much to replace it so I dont think its that hard, but Im` sure you`ll get more specifiuc answers from th400 owners that have actually done it themselves...

My regular mechanic wouldn't do mine and had to take it to a tranny shop. Was leaking around selector shaft and speedo. I am told one of them takes a special tool to do, but both were done for $70 so I didn't want to even bother with it.

I just replaced the one on my TH400. In order to change the seal (it is a seal not an o-ring) around the selector shaft required you to drop the pan and remove the shaft to get the old seal out. Wasn't hard, but I had the trans out of the car at the time.....shouldn't be a big deal to do it in the car either.