7 1/4 to 8 1/4 rear end

[BudW]

Half tons are 5x4.5" until 85 or 86 I think, and them go to 5x5"

Correct.


'65-67 differential housing is almost a perfect fit for FMJ.
59.500" drum to drum
54.250” flange to flange
44.000” center of perch to center of perch

The differential is 1" wider (1/2" per side) and perches are 0.230" narrower (per side - which is almost negligible).

The big issue is those '65 axles. You have to get rid of those axles - for doing brake work on a normal basis is almost impossible (as well as finding brake drums). Getting '66-67 axle shafts is somewhat easy to find.

That said, I would love to get my hands on that differential - if you are not.

 

[80mirada]

I was toying with getting a 9.25" out of an early 80's D150 or a late 70s B or R body.

 

[BudW]

I don’t have data on the early ‘80’s D150 (yet) – but would “guess” it would be the same as ’72-74 8¾” – but unconfirmed.
The early and late ’80’s 9¼” are the same except for the axle shafts (different wheel bolt pattern).


'71-79 B-body, ’79-81 R-body and 75-78 C-body perch placement are the same (same dimensions if 8¼” or 9¼”, including driveshaft length). Details are:
drum to drum – is not known – but thought to be 62.0” or 63.0”.
57.625” flange to flange (B and R body 8¼” or 9¼” only)
57.734” flange to flange (8¾” only)
57.875” flange to flange (9¾” (Dana) only)
59.200” flange to flange (C-body (all) and '75up B-body station wagon)
57.625” flange to flange (71-74 8¾” station wagon)
44.000” center of perch to center of perch (for all mentioned above).

 

[rcmaniac791]

Truck one you're gonna have to replace the axles, drums, and who knows what else. Trucks were 4.75 bolt pattern so your existing wheels won't fit.

That's way more than what I want to get myself into. The search continues. fortunately, I'm not planning on swapping for several years.

 

[jamf]

The trucks were never 4 3/4 bolt circle. Either 4 1/2 or 5 1/2. A truck housing is a little wide though. Unless its a super deal, I'd keep looking for something narrower.

I had a 68-70 b body 8 3/4 in my car for many years with a set of 11x2 1/2 drums and backing plates from a '77 W100.

Around $2k will get you a new, ready to bolt in Dana 60. Or you can build your own from an old truck rear and have around $800-1200 in it.

 

[rcmaniac791]

Around $2k will get you a new, ready to bolt in Dana 60.

sounds like a pretty good deal to me.

One last (silly) question: can the stock rear-end handle the occasional burnout, or should I never even try?

 

[BudW]

In my opinion, it is easier on a differential to perform a burnout, than it is for tires to “hook up”.

The exception on that is if only one rear wheel spins, then in that case, the solo tire is going twice the speed of the speedometer and that is also hard on the spider gears (working overtime).

If you have a problem with one tire spinning, then you also need to look into upgrading to limited slip.
BudW

 

[Idle Ender]

Old thread, but going the Jeep Liberty route is cake. Did it myself with no real issues. Just grind the old brackets off and weld new perches on. Then all you need is a driveshaft. No modifications needed for the brake system to run disks. (except new e-brake lines, which I havnt gotten around to yet) If you run 14" wheels, youll need to grind the calipers down like I did, or jump to 15" to clear them. In the end, the rear sits significantly wider than factory but still well within the fenders. Honestly, it looks better.

 

[80mirada]

How close are the dimensions of the Jeep Liberty axel to the FMJ axel

 

[Idle Ender]

A good couple inches wider, I believe. Id have to look. But not enough to look out of place. Just make sure your spring perches are measured up right and youll be good to go. You have to remember that modern wheels run a completely different offset than old stuff to clear the brakes and whatnot. The extra width on the axle makes up for it and the Jeep ends up with an almost identical width as an FMJ while still having a longer axle.

 

[brotherGood]

Liberty or cherokee?

 

[Idle Ender]

Liberty.

 

[brotherGood]

I didn't think the liberty interchanged.

 

[BudW]

The spring perch is on wrong side (top vs. bottom).
I've heard these might fit - but have no measurements yet to place in my spreadsheet.

 

[Idle Ender]

Ill post pictures later, but the Liberty rear needs all mounting stuff ground off and new perches welded on. Its not exactly plug and play, but it works. Have it under my car and running now. Liberties have coil springs in the rear, so all that has to go.

 

[Idle Ender]

Wrote something up about the swap.

Jeep Liberty 8 1/4 rear swap