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MJ differential swap questions


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I've been looking into replacing my differential for a while and have been really tempted to throw a mopar 8 3/4 on my MJ, I know there are other options out there (I've already searched) but I love the idea of the drop out center section,just out of curiosity I know if I get an 8.25 or any other diff off of an XJ I have to flip and relocate the spring perches but would I have to mess with the shock mounts as well? is there any one here that has done the 8 3/4 swap to there MJ? thanks.

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I just did an 8.25 swap. The perches need to be moved. Also, the shock mounts are different from XJ to MJ. The MJs shocks are both located on the same side, where the XJs have one on one side and one in the other. It's a pretty sttraight forward swap.

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Cool, I was thinking if I had to go through the trouble with the shock mounts swapping the diff from an XJ diff to the MJ I would stick to my plan of installing the 8 3/4 I know it might be a little too much for what I have now but I have some serious plans for that truck down the road

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But the lower shock mounts are on the spring plates. So if you're staying SUA, the shocks would mount up just the same as before. You could just cut the shock mounts off the 8.25.

Good catch I went SOA so I ditched the stock spring plates

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OP- 8.75s and 9.75s in my locale are hard to come by and the couple that I found were $350.

 

I never did find the correct width either and the one that I measured was 63" hub to hub, which might have been OK.

 

But when I figured re-gear and other costs...........screw it.

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But the lower shock mounts are on the spring plates. So if you're staying SUA, the shocks would mount up just the same as before. You could just cut the shock mounts off the 8.25.

Good catch I went SOA so I ditched the stock spring plates

 

But you didn't have to. You could have just flipped them from one side to the other and reused them. That would also have allowed you to keep the same shock absorbers.

 

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OP- 8.75s and 9.75s in my locale are hard to come by and the couple that I found were $350.

 

I never did find the correct width either and the one that I measured was 63" hub to hub, which might have been OK.

 

But when I figured re-gear and other costs...........screw it.

I see 8 3/4's often in my area, not too expensive and I really don"t mind if I don"t find the more sought after 489 carrier as long as It's not the type with the pressed on drums I figure it would be cool to be able to swap rear gears very quickly and the added strength to boot. 

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My next MJ rear swap will be a 8.8. Dealing with putting disks on a axle is a expensive ordeal if you are forced to use new parts.

 

(Referring to the 8.25 I swapped into my MJ and used ZJ discs with all new parts except for backing plates and caliper brackets)

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Consider rear discs too.

:thumbsup: might as well, I'm pretty sure its a direct swap from the 8 1/4

 

 

 

Is that true?  I have a set of disks I took off my 8 1/4, that originally came from a D35.  I was going to sell them, but if its a direct swap, I'll put them on the 8 3/4 under my Duster.

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Consider rear discs too.

:thumbsup: might as well, I'm pretty sure its a direct swap from the 8 1/4

 

Is that true? I have a set of disks I took off my 8 1/4, that originally came from a D35. I was going to sell them, but if its a direct swap, I'll put them on the 8 3/4 under my Duster.

The KJ Libby's had rear disc breaks. There was a write up on here. It was straight forward XJ 8.25 drums to KJ 8.25 discs

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Consider rear discs too.

:thumbsup: might as well, I'm pretty sure its a direct swap from the 8 1/4

 

 

 

Is that true?  I have a set of disks I took off my 8 1/4, that originally came from a D35.  I was going to sell them, but if its a direct swap, I'll put them on the 8 3/4 under my Duster.

 

Yes it is true you can use the rear brake set up from many jeeps with the 8.25 rear and since the 8.25 and D35 swap over easily it will install on the 8.75,the only issue I've heard of is when you want to install the drum brake combination for the parking brake on the 8.75 I've read it requires a lot of custom work but then again that can vary according to the persons ability.

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