Axle Swap

I own a 1970 CJ5 and I might be able to get a front axle off of a 1978 CJ5 that has disk brakes which I would really really like to have. My question is would the 78 be a good donor if not why and what would be involved to make it work if it's even possible? He has the rear axle as well but I'm not sure why I would want it possibly gearing? Looking forward to seeing your responses.

Thanks in advance.

 

The rear axle from the '78 would be a big downgrade. You don't want it.

Swapping in a later Dana 30 axle with open knuckles and disk brakes is a common upgrade for these Jeeps. But you will have to regear the axle. A '70 will have either 3.73:1 or 4.88:1 gears, and neither of those ratios were offered in 1978.

Other than that, it's mostly a bolt-in swap. You will likely have to install shims to make the caster right. And you will need a master cylinder for a disk-drum system (IIRC a Corvette MC is a popular choice). You may want a proportioning valve for the rear brakes.

This topic has been covered a lot in earlier posts. Searching old posts is tough right now, due to the change to a new server.

 

I used a 78 for my swap. I took the time to go through it before installing which was fairly easy and well worth the time. I'm still using the original master but you need to read up on the braking system - there is a lot of info here and other places. I first tried it without the caster wedges and it didn't work - almost couldn't keep it between the ditches! I'm using something like 5 degree wedges now.

One thing I've noticed is that with the double hole setup on the steering hub, the tie rod has to move back and forth farther to get the steering angle. For my (power) steering setup this required a longer pitman arm.

Other things to consider are spring plates, U-bolts, and shock placement.

It's a great swap but it's not as easy as it sometimes sounds. To an experienced guy it is easy. To those who've never done stuff like that it's a bit more challenging.

 

With a one piece axle swap the Model 20 is not really a downgrade from the Dana 44. Especially true if he doesn't have the 1 piece axle 44. And axles are cheaper than a regear by a long shot. But if you have the 44 with the one piece axles then I would suck it up and regear.

 

Sorry but I must disagree. While the tapered shafts are not as strong as a one piece shaft the 20 housing is weaker, the tubes are thinner, has smaller axle bearings, and the drive pinion uses a collapsible spacer instead of solid shims to set pinion bearing preload.



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That and the fact that the '70 has an offset rear axle and the 20 is centered.

 

Most are centered except Quadrac equipped CJ-7's. These were offset to the passenger side and narrow track. The spring pads must be moved.

 

In his application the housing strength doesn't appear to be a major factor, and of all of the 12 bolt Chevy's I have broken not a single one was due to the crush sleeve. I've built at least 3 ten bolts that ran deep in to the 10's in 3500# race cars and the crush sleeve is a non issue. I've built 12 bolts with a sleeve that had to be shimmed for preload, and in my experience it just added to the time to setup preload. The model 20 gets hammered on a lot, and realistically, it's no worse than a lot of the others out there. The early 44's also have tiny little axle tubes compared to even a 1/2 ton truck. My buddy's '79 CJ-7 with a 304 and a Quadratrac pulled the left front wheel 6" off the ground when street racing it in low range and would smoke the tire all the way through second gear on the asphalt. And the first thing he broke was the Dana 30. While in the mud.

 

Well, I've re-tubed at least a dozen AMC 20's with 3/8" wall dom tube because of bent tube issues. many times the bend was outside the spring mounts.
I've replaced at least 6 or 7 sets of 10 bolt ring and pinion gear sets due to collapsible spacer failures. Several sets of 12 bolt gears for the same reason.
The collapsible spacer replacement certainly is not a down grade and is much easier to set up than messing with a crush sleeve, even if it takes slightly longer to do. There's no denying it's stronger. I won't set up a 9", Toy 8", 10 or 12 bolt without using the solid shim conversion. For $23 it isn't worth not doing.

But, we're not talking about 10 bolt or 12 bolt 1/2 ton axles are we? We're also not talking about Dana 30 front ends.
The subject was the AMC Corporate 20 axles used in CJ's.
The tubes are still thinner and weaker than an early 44, the carrier is thinner and weaker and prone to bending where the tubes are pressed In, suffer from weak rosette welds there, have small axle bearings, etc, etc.


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Simply put a CJ 20 isn't worth the gas money to drag home. I think I have posted that same phrase several times......