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Old 01-08-2004, 09:51 PM
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Driveshaft measurement

Thanks for all of your help with getting me through the rear end process. Got to fix a bleeder valve problem but after that I have to measure for my driveshaft. I have a couple questions.

The difference in lenght between the driveshafts for the 8 1/4 and 8 3/4 rear end is less than an inch i believe. In fact when I put my old driveshaft from the 8 1/4 in and put it up to the 8 3/4 it seemed to come rather close.

When you slide the driveshaft in the trans, how far does it have to go, and can you leave it more in or out, so a new driveshaft won't have to be prepared for the slight difference in lenght?

If not, how should i measure for a new one.

And since my driveshaft fell out while driving should I replace anything in the trans where the driveshaft goes in?

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Old 01-08-2004, 10:11 PM
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Here is a good site with proper measuring directions.

http://www.iedls.com/measure.html

Vince
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Old 01-08-2004, 11:04 PM
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71gtx,
You only need to worry about two things with the drive shaft.
The first is that it is not too short that when the rear end drops into a pot-hole the shaft falls out of the transmission.
The second thing to watch out for is when the rear end goes up like when you hit a speed bump. If the shaft is too long it will get JAMMED into the transmission's rear seal so hard it will tear it out of there.
So be sure the splined slip shaft is mid way of it's total travel. Then measure from the center of the front universal joint to the center of the rear u-joint then subtract the diameter of one of the bearing cups and that will be your drive shaft length.
Have fun
Scholman
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Old 01-09-2004, 02:49 PM
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scholman,
If the difference is very minimal between shafts (my old rear end needed a slightly longer driveshaft than the new) can I just slide the slip in a little more and use the same shaft? I guess what I am asking is how much does the slip move in and out of the trans with bumps. and would i be ok? The slip on this driveshaft is decently long.

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Old 01-10-2004, 08:01 PM
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The in out movement on the yoke is dependant on the angle of the shaft and the total suspension movement. Low angle and small travel is very little movement. Higher angle and bigger movement is more travel None of my vehicle yokes move more than 1/2" maximum.

Trees
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Old 01-11-2004, 11:10 AM
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What is odd is this:

I measured my slip today and it is 7.5" long. According to internet sites, the rear end centerline to yoke for the 8 3/4 is only about .5" more than my old rear end. That would mean my driveshaft needs to be only .5" shorter.

Now I would think that the old rear end caused the slip to be centered 3.5" into the trans, if it was stock. However when I stuck the drivshaft in to see if it met up with my new rear end, only .5" or so of slip was showing, meaning 7" was in the trans. Why would this be, and will I need to have the driveshaft customized? How much does the slip move in and out when you hit a pothole or bump?
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Old 01-11-2004, 12:00 PM
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71, sounds like you have a no brainer. You could cut an inch off the sip part of the yoke and be in great shape. Now I don't mean take a hacksaw to it. Its pretty hard stuff. If you don't have a lathe to do it, take it to a machine shop so it will be true and they can put in the same chamfer as the old (inside to protect the shaft and outside to prevent damage to the new seal when you slide it on).. Second choice would be to hit the yards for the same yoke, only a slightly shorter slip length.

Trees
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