Rear end, driveshaft questions...

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2112

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I have just bought new axles for my 8 3/4 swap. I have been doing a lot of reading and I'd like to make sure I have things right.
From my understanding swapping a 8 1/4 for a 8 3/4 with a 904 tranny I will need to shorten the driveshaft 2 1/4". Does that sound correct?
Also I have read that It is a good time to upgrade the yoke. What yoke do I upgrade too? ?? Would I need new u joints then as well? Which ones would I get? Do I have to upgrade the yoke? What purpose does that serve? Also I seem to be missing the bolts, and the covers that hold in place the U joints on the case. Does anyone know where I could find them?
I think I have covered everything? I hope! Thanks for all your help guys!

BTW, I have a 360 with around 400hp, 904 transmission, and a 489, 3.23 sure grip that I am trying to install... correctly :)

Thanks.
 
going from 8 1/4 to 8 3/4....

where do you get 2 1/4 inches shorter at?
 
sure your not changing from a 7 1/4 and why not keep the 8 1/4 with an automatic?I'm sure it would hold up fine.400 HP - 904 - 3:23 gears?Should be 400 HP - 4 speed- 3:55 gears when using the 8 3/4.
 
Hmmm... I never saw that chart. Maybe I'll try to use the axle as i's then? What about upgrading the yoke??
 
the yoke on the 8 3/4?

which case do you have.....and even it is the smaller 7260...

i got a couple of race cars that use the smaller 7260 yoke and u-joint....and never had any problems with them.
 
They way it sounds then is that everything should just swap out? I have the 489 case.
 
Check end play on the slip yoke at the tranny with the suspension at full droop to make sure the output shaft is not bottoming in the yoke. You may find it needs a half inch or so shorter shaft. They will probably run like that without enough clearance for quite awhile until something gets beat to ****.
 
2112, you would shorten your driveshaft 2.25in only if you were changing from a
7 1/4 to an 8 3/4 rear. I can't remember the difference for an 8 1/4. Orv
 
Avoiding to that chart that was posted .066" would be right.
I'm going to try it without shorting and see what happens. How do you get a full load on those rear springs to check it though?
 
Jack up the rear and put jack stands under the rear. You do want to make sure the slip yoke is not bottomed out when on the suspension. If it's too tight you will damage the tailstock on the trans. 1 inch travel is good.
 
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