inner drive axle

It really depends on what's causing the vibration. A dry CV joint will eventually seize, sometimes with catastophic results.

I'd say you need to get under there and take a good look. Inspect the CV boots (the outer joints, near the wheels) and the inner joint boots. Any of them split?

If it changes when you're turning, isn't that more logically the CV joint than the inner drivers? I don't know that the geometry on the inners knows that you're turning, so if steering changes it, it's more likely to be something that knows you're turning (the CV joints).

If it's the CV, it will fail at some point and you Won't Go Anywhere. At All. If that's not earth-shattering for you, and you're feeling adventurous, go for it, but I'd do it now if it were me.

One way to make sure you know which side, and which joint, is making the noise, is to jack up the front of the car & put it into neutral, spin the drive-wheels. Listen to it with the steering wheel straight, and then turned to each side, see if/where you can induce some noise.

Good luck, Dave Hinz

Dave and Grunff, thanks for the replies. Acting on your advice I took it to my local Saab guru. It turned out to be the driver where it enters the transmission, and also the tripod joint. He also mentioned he would refill the transmission with synchro shift, which is supposedly a good thing (and sanctioned if not recommended by Saab). And lucky for me, he says he can get a new driver at a significant discount (though I have to wait for it to come in from California). All told, it should be a ~$600(US) experience... unless they find that the other side is worn also...

John

Usually the right hand side goes before the left, especially on turbos - because of heat from the exhaust.

I have to say, I've never needed to replace them. On my T16 they were a little worn, so I switched them side to side. This presents freash wear faces to the tripod bearing.

Grunff,

Having not seen the transmission driver with my own eyes, I'm not sure how worn it was. For all I know it may have been too worn to swap sides. But I'm content paying for a new one (rather than switching them), since I'd have to pay for the labor if they fail again before I can afford a garage :)

The car is non-turbo btw.

John

Well, it's done. New transmission driver, tripod bearing, and assorted seals. All told $420 US in parts (including $75 worth of Synchro Shift). The cold weather shifting is definitely improved-- especially the 1st -> 2nd, which was a bit hairy in the cold before. So it's even more of a joy to drive. :) I figure this should increase the probability of my transmission having a long life.

John