J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is involved?

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jay-ten
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J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is involved?

Post by jay-ten »

I’ve heard of people doing this type of swap and thought it sounded like a good idea.
I’m looking for first-hand experience on what is involved with this and things to know that I did not think about.
Is this a plug and play bolt on swap or does this require bracket moves, welding etc.
Are there year compatibilities or will any J20 axle assembly work.
What ancillary equipment should I get with the J20 axle assemblies?
Axle assemblies – are the locations of the differentials the same between a J20 and the W/T Cherokee. I’m sticking with the Th400 Quadratrac. I thought I read somewhere that the J10s differentials were in a different spot.
Springs – The J20’s are ¾ ton right? Are the J20’s the same height as the Cherokee W/T or will there be an increase in ride height of the Cherokee W/T with the swap if I include the springs? Are the springs plug and play bolt ons?
Drives shafts – are the J-20 drive shafts stronger? Are the U-joints the same? Will the J20 axle assemblies bolt directly to the W/T Cherokee drive shafts or should I get the front and rear drive shafts with the J20 axle assemblies.
Brakes – The fronts are disc and the rears are drums on both right? The rear axle swap would include the drums so the bolt on point for the rear brakes would be the brake line. For the front axle assembly swap are the disc diameters the same? If so, I could just slip the W/T Cherokee calipers onto the J20 disc. Or should I just get the J20 front calipers with the front axle assembly? If I do that, the bolt on is at the end of the brake lines.
Other – tell me what I might have overlooked with the swap
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derf
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Re: J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is invol

Post by derf »

Most important thing is to get a 70's era donor. If you get a 1980-88 donor the front axle will have the differential on the wrong side. And make sure the rear axle is set up with the offset differential for the quadratrac. Not all of them were. If those two things aren't right, you will have a heck of a time getting it to work.


Front axle is more or less a bolt in. Everything should line up. The J20 tie rod and drag link should be kept (or replaced with new J10/J20 spec parts if they are worn out). The driveshaft will bolt right up.

The rear axle will have it's spring pads and shock mounts in the wrong location. But those are easy to cut off and weld back on in the right location. The springs themselves may be taller from the J20 but the location of the spring eyes should be the same. Though if your donor is older than 75 or 76 it will have the post mount springs and those aren't compatible with your 79. The U-bolts for the rear axle are bigger because the axle tube is a bigger diameter. It's hard to find a set of replacement bolts and you'll have to do some digging to find something compatible. I think mine are specified for a Ford F250. And be sure to keep the spring plates that the U-bolts go through too. Those are specific to the J20 and match the diameter difference.

The rear axle uses the same 1310 U-Joint as the Dana 44 under your Cherokee. However, the pinion is longer (sticks farther forward) so you may have to shorten the rear drive shaft.

Front brakes starting in 76? were all discs. Before that drums were a possibility I believe. The front calipers should be the same. However, you can take the opportunity to upgrade the brakes with better parts for not much money. The J20 axle is compatible with the 3/4 ton Chevy. They offered a brake upgrade (JB7 build code) in the 80's that had slightly bigger rotors and bigger calipers. If you go buy the Chevy parts at the parts store, you can get them for pretty cheap compared to aftermarket upgrades. The rotors go on easily and the calipers bolt right up with no mods. I did that upgrade on my J20 axles. Besides, swapping out your old rubber hoses on the front is not a bad idea to do while you swap out the calipers.

The rear drums should hook up just the same as the original axle. Parking brake cables will attach to the frame exactly the same, although they will probably be a lot longer than they need to be. The hard lines for the brakes meet in the middle and have one line going up to the frame from there. I'd keep the hard line on the donor axle and swap out the rubber hose for new when you do the swap.

Wheels, of course, will have to be changed to the 8 lug pattern.

You may want to swap out the speedometer gear in the transfer case to match the gear ratio and tire size you're going with. The J20 axles would have 3.73 or 4.10 gears from the factory. The Cherokee would have 3.08 or 3.54 most likely.

That's all I can think of off hand.
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Cecil14
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Re: J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is invol

Post by Cecil14 »

The J-20 rear D60 is going to be quite a bit wider than the stock W/T Chero rear D44. I don't recall offhand how much wider, but it is significant from what I recall.


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank

Topic author
jay-ten
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Joined: Sat Jul 01, 2017 6:09 am

Re: J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is invol

Post by jay-ten »

Wow you guys are awesome!

fsj454
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Re: J20 front and rear axle assemblies swap into 79 Cherokee Wide Track W/T with TH400 and Quadratrac– what all is invol

Post by fsj454 »

Hi jay-ten . I have done all of the above,. Where is your location because I have all the parts rims .axles .shafts. .From a 1979 j20 3.73 ratio matched set of diffs. Dana 60 rear. Dana 44HD front. Extra thick axle tubes from factory. All parts are inside out of the weather . These parts are getting hard to come bye so get them when you can NEED ROOM ........
:fsj:454.nv4500.205.twin stick.hydo boost. hydrolic clutch.dana 60s.soa.37s 17inch.tration bar.warn 1200. 4 wheel disc.aero29 gallon .conferr roof rack.spal pulse width modulation.spal duel fans.painless battery isolator.duel batterys.factory cb. headers 2 1/2 duels.4.56 Detroit locker.alloy 35 spline axles.stainless brake lines .holley 770.edelbrock.fuel.water.intake.H4s.head light relays.racho 9000 shocks.rock ram.steering box brace.j20 steering box.msd8265 probillet distributor.msd super conductor wires.
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