Ok, the tranny swap is in an '81, 3 speed manual to super T-10. Can I just subtract the difference in tranny lengths from my existing driveshaft length, and go buy a used driveshaft that is that new length? It seems that used driveshafts are a lot cheaper than having mine shortened and balanced. I would like to have the driveshaft ready to go when I do the tranny swap to minimize car downtime.

Thanks,
Clay

I would check with a drivshaft shop and see where they measure from.Some shops use different measurements.I measured mine frome the machined surface on the rear of the trans(where the seal is right on the back of the trans)to the machined surface on the yoke of the rearend.

Thanks. I did some more measuring today, and I have a 48 1/2" driveshaft. The new tranny is only 1/2" longer than the current one, and I have 3 1/8" of yoke sticking out the back of the tranny (from back of tranny to center of u-joint). I am beginning to think that unless the yoke I get for the super T-10 is really long, I may not have to shorten the driveshaft at all.

If your interested in a new try Denny's drive shaft service. They did right by me and at a good price.

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Second place is the first LOSER!

I think Denny's or one of the other big name co.s had some mearuing info on their website, check it out. From what I have been told you can go up to 3/4 shorter, any more of a difference and you want to get it lengthened. If the new tranny is longer, you have to check it, under rear suspension movement (accelration) you will push the yoke into the tranny output shaft.

We'll watch the length carefully. I noticed that there is 3 1/8" of yoke sticking out of the back of the current tranny (back of tranny to center of u-joint), so I am hoping that we will be ok. We also raised the rear end recently and that pulled the yoke out some from the tranny. I guess once we get a yoke for the ST-10 I can make some measurements. I hear that it should be pushed into the tranny all the way, then pulled out about 1". Maybe it will end up at no more than 2 5/8", then it will all be a wash on the driveshaft length.