[71gtx]

I am swapping an 8 3/4 rear end for my current 8 1/4 rear. One difference that I noticed was on the spring perches.

On the 8 1/4 the center hole on the spring perches is very small, enough for the nipple on the leaf spring to snuggly fit in. However, on the 8 3/4 the center hole on the spring perches is 4 or 5 times that, so that the nipple has way too much playing room.

Do they make different nipples that you can bolt in? or, when you put the u-bolts on will this problem not matter?

[TooMany2count]

what I have done is after ya unbolt the rearend is clamp the spring together, remove old centering bolt & use a regular hex head bolt for the centering bolt. the hex head will take up the extra room & as you tighten the u-bolts on the rearend the hex head will be pushed into the hole.............joe

[71gtx]

The old hole measured roughly .5", whereas the new one measures 1.5". Are you saying to use a bolt with a 1.5" hex head to fit snugly?

[sc3148]

It sounds like the 8 3/4 was originally equipped with rubber spring insulators and special center bolts, this is why you are seeing such a large hole. Unfortunately they don't make center bolts to make up that much difference. Your choices are as follows.
1. Find a set of original insulators & center bolts off the 8 3/4 and hope the spring packs are close in thickness.

2. Weld on a set of perches that accept your center bolts.

3. Have a machine shop make a set of bushings to take up the difference between 1.5 inch perch hole and the center bolt head.
Good Luck.

[TooMany2count]

Originally posted by 71gtx
The old hole measured roughly .5", whereas the new one measures 1.5". Are you saying to use a bolt with a 1.5" hex head to fit snugly?

damn thats a BIGGGGG hole, here's whats ya do. either remove the spring perch's from your old rearend & weld them to your's OR go to your local Mopar dealer & ask for part #P4120074 those will be new spring perch's & they only cost about $15 for a pair and then remove your old ones & weld the new ones on. BUT be sure to keep your angles the same as your old ones when swapping them out or your pinion angle will be off & you'll have BIGGER problems................joe

[71gtx]

Well the re-welding the spring perches is something I DONt want to do. The reason behind is i drove 9 hrs for this new rear end, whereas I could have got a different length housing near my house where I would have to weld the spring perches anyways. So, I would like to try something different.

I will load up some pictures tomorrow morning for everyone so you can see my picture more clearly.

Thanks

[poncho62]

This rear end project has NOT been fun, has it?

I would get a thick washer or collar made uo to take up the difference.

[TooMany2count]

then get yourself some 1.5 round stock & measure the head of the centering bolt & drill a hole in the center of the round stock. OR get some 1.5 outside diameter pipe & see if the hole maybe the same as the centering bolt.........joe

[71gtx]

No this has been a project from hell. Seeing after i got ripped off once and now have a problem with this one.

But maybe now that I think about it I can find a thick heavy duty washer that has a center hole of around .5" and is 1.5" round. I'll go looking today for one. Like you said poncho.

Still looking for digital camera, I will definitely post pictures by tomorrow.

Oh, not to mention one of the axles is missing some studs. I've never dealt with installing those, any suggestions?

[71gtx]

Ok, here's a picture of the new spring perch. My old one had three holes the sizes of the small two in this picture. Come to think of it, when I unbolted my rear end, I did not check to see which hole it was in. But it was probably factory and since it centered nicely, I am pretty sure it would be the center one.

[Crazy Mopar Guy]

Was that diff ever in a late model car? My 1980 Cordoba LS was a stock 8 1/4" rear, when I tossed an 8 3/4" B body diff I had to open up the spring perch hole to what looks like the size of your attachment pic.
Either the perch needs to be changed or you'll have to fill the void with drilled bar stock etc as the other posters have said.

Are the spring perches the same distance apart as the old diff?

[71gtx]

Yeah, they both measure 47 inches away from each other. They are both the same sizes, mine is a 71 b body, the new rear end is off of a 73, so maybe they changed that part in that year. I think I will call up a local spring shop tomorrow and have them make me a bushing. I'm sure they know what is going on.

By the way Crazy Mopar Guy, did you have the same problem as me then? What did you do?

[poncho62]

You could always weld a piece of steel plate over top of that one with the right sized hole in it.

[Crazy Mopar Guy]

Originally posted by 71gtx

By the way Crazy Mopar Guy, did you have the same problem as me then? What did you do?

I actually had the exact OPPOSITE problem you are facing, I just opened up the size of the hole on the perches to fit my spring locator size.
I would take a good look at the pinion angle before deciding what to do, if the pinion angle isn't close it might be in your best interests to cut the perches off and have new ones welded on, even if it does seem like a pain in the butt. If the pinion angle looks close, I would just give a look at filling the empty space around the pin?

[71gtx]

I understand exactly what the pinion angle is, but how exactly do you measure it?