I've done the swap twice. 1.75" is a what I have used.
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| Swapping 8.75 in place of 7.25 https://slantsix.org/forum/viewtopic.php?t=48328 |
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| Author: | roadrunnerh [ Wed Mar 28, 2012 5:43 pm ] |
| Post subject: | Swapping 8.75 in place of 7.25 |
Hello folks, hopefully someone can help me out. I am swapping a 8.75 in my '75 Scamp. I found out The axle centerline to yoke/universal centerline is 12.35" for the 8-3/4" axle. What is the axle centerline to yoke/universal centerline for a 7.25? I need to know how much I need to shorten my drive shaft. Thanks for your help! |
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| Author: | slantzilla [ Wed Mar 28, 2012 7:08 pm ] |
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I've done the swap twice. 1.75" is a what I have used.
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| Author: | roadrunnerh [ Wed Mar 28, 2012 8:27 pm ] |
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Thanks for the response! According to this page http://www.mymopar.com/axledims.htm 7.25 dimension is 10.09" so, with the 8.75 measurement being 12.35" I come up with 2.26" as the measurement the drive shaft needs to be shortened. How engaged is the slip yoke in your tranny? Or are these numbers wrong? Now I'm confused..... 
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| Author: | roadrunnerh [ Fri Mar 30, 2012 5:03 am ] |
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Slantzilla, how did you arrive at 1.75? Not saying you are incorrect, just asking. Anybody else? Only one person has done this swap on here??? |
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| Author: | 1974duster kev [ Fri Mar 30, 2012 6:12 am ] |
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I did the swap it was something like 1.75 or 2inches don't really remember you have a bit of wiggle room to get it to work. Kev |
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| Author: | roadrunnerh [ Fri Mar 30, 2012 6:42 am ] |
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I was wondering how much you can pull out the tranny slip yoke and still have enough engagement in the tranny. You want it engaged as much as possible for the most strength, right? |
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| Author: | Doc [ Fri Mar 30, 2012 10:11 am ] |
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Yes... Keep the yoke "deep" into it's receiver bushing for the best support. I always install the new rear axle assembly and then measure, to get the correct driveshaft length. DD |
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| Author: | 1974duster kev [ Fri Mar 30, 2012 11:46 am ] |
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Thats what I did, I put the 8 3/4 in then measured what i needed to lose off the drive shaft Kev |
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| Author: | Doc [ Fri Mar 30, 2012 12:11 pm ] |
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Just remember that the rearend assembly needs to be at "ride height" when taking the driveshaft length measurment... don't measure while the rear is "hanging" in the air. DD |
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| Author: | slantzilla [ Fri Mar 30, 2012 2:49 pm ] |
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Quote: Slantzilla, how did you arrive at 1.75? Not saying you are incorrect, just asking.
Because that was the number that put the yoke 1" out of being bottomed out in the tailshaft.Anybody else? Only one person has done this swap on here??? I did the 2-1/2" on the first one I did and it is too short. The yoke is almost 2" out in the tailshaft. That is good for a little while, but it will beat the tailshaft bushing out eventually. |
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| Author: | roadrunnerh [ Fri Mar 30, 2012 5:59 pm ] |
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Ok fellas, what am I missing??? If the difference between the axle center and yoke center is 2.26" (assuming that is correct) why not go with that number? Slantzilla, are you saying that the slip yoke for the tranny should not be in as far as it goes? It should be 1" out of bottoming out? |
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| Author: | slantzilla [ Fri Mar 30, 2012 6:13 pm ] |
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Yes, that is correct. If you bottom it out it will break things in the trans as the rear suspension goes through it's gyrations. |
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| Author: | roadrunnerh [ Fri Mar 30, 2012 8:08 pm ] |
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Confusing. Someone says keep the yoke "deep" in the trans, someone else says keep it backed out 1"..... With the suspension moving, wouldn't that be up and down rather than forward and backwards? Again, not trying to be difficult (and I really appreciate the responses) I just want to get this right. |
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| Author: | zorg [ Fri Mar 30, 2012 9:50 pm ] |
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Quote: Someone says keep the yoke "deep" in the trans, someone else says keep it backed out 1".....
The yoke is several inches long, so backed out only 1" is still fairly 'deep' in the trans bushing.Quote: With the suspension moving, wouldn't that be up and down rather than forward and backwards?
At normal ride height, the differential is several inches below the trans. tailshaft. So when the suspension compresses, and the diff. is now at the same height as the trans., the distance between the two is now shorter. The way this slack is taken up, is by the yoke sliding further into the trans. If the yoke started all the way in, and the suspension tried to compress, something would have to give... Does that make sense?As far as the perfect amount to take off the driveshaft? I don't know, I'm am planning to do that swap this summer. |
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| Author: | roadrunnerh [ Mon Apr 09, 2012 1:42 pm ] |
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Not trying to argue with ya, but no, that doesn't make sense. The pinion yoke and tranny yoke are different heights. Got it. When the suspension compresses, and the height is closer to equal, it still will be the same distance between the two.....kinda like a hinge. There would be no force pushing the rear closer to the tranny. |
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