Jeep Full Size Axle Swap - Full Width

"We decided to swap our M-715's front Dana 60 and rear Dana 70 for a front Dana 60 and a rear Dana 70."

Everyone who heard us utter that line in the past few weeks gets this confused look on their face, and then says "Huh? Why?" On the surface, it just doesn't make much sense. What we wanted was a heavier-duty pair of axle assemblies for our military truck. So why swap in the same axles it already has?

While the stock axles and the new axles have the same model numbers, there are virtually no parts that interchange between them. The M-715 was the one of the first vehicles with a Dana 60 and Dana 70 under it. In the 40-plus years since our truck was designed, metallurgy has improved, gear sets have become more standardized, open knuckles have become the norm, and drum brakes are no longer the only type of brake available.

When we got the front Dana... 

   

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When we got the front Dana 60, we didn't know what it came out of; all we knew was that it was missing all the passenger-side components and that it was a high-pinion axle. Heck, the guy we got it from didn't even know what a Dana Bill of Materials number was, so until we saw it we didn't really know what we were getting. Still, for $300 when we knew we'd want dually hubs anyway, it wasn't that bad of a deal.

By all rights, our axles should have given up the ghost a long time ago. Our M-715 weighs 6,500lbs normally, and once all the tools from our roll-away tool chest, camping gear, grill, cooler, spare parts and everything else is in the truck for a weekend campout, it's more like 7,500-8,000lbs. On the bright side, it rides a lot nicer than an empty M-715 does. On the downside we can practically hear our stock axles screaming in agony every time we feed that big-block some gas.

A goofy bolt pattern, closed front knuckles, and drums that get out of whack every time we went in the mud were but a few burrs in our side. Add to that a limited gear selection, an offset rear axle, and limited parts availability when out in the boonies and we'd had enough. Check out the sidebar for the head-to-head comparison between the new parts and the old parts.

Any way you cut it; building a Dana 60 front axle isn't cheap. We want our truck to retain its military look when we are all done, and by using parts that many guys don't want, we are aiming to keep costs down. To keep the military look, we are planning on running HMMWV wheels and tires, and the big backspacing of those wheels will necessitate wide axles to keep the tires out of the frame and springs.

The ball joint front Dana 60 isn't as popular as the kingpin axle, so we were able to score most of an axle for $300. Most guys build these axles for 65 to 70 inches WMS to WMS. The 715 axles are around 72 inches wide so we knew we'd need something wider than what most guys ran, especially with using those HMMWV rims, which meant building a dually-width front axle.

To build a heavy-duty rear axle, as many of you know, is way cheaper than building a front Dana 60. Only select 1-ton trucks came with front Dana 60's, while all 1-ton and even most 3/4-ton trucks came with beefy full-floating rear axles. So, thanks to more of them laying around, it is cheaper and easier to build the rear axle. We went with a Dana 70HD out of an '87 Chevy dually because of the ultra-wide width we were aiming for.

It isn't until you drag a part home and start working on it that you really start learning about it, and we literally just pulled the rear axle out of the junkyard before sitting down and writing this. You can do all the internet searching you want, but in the end, nothing beats hands-on experience. While it will be a few months before we've got these things built and slung under our truck, here's some of what we learned while wrestling a pair of 500-lb axles.

By doing an internet search...        read full caption By doing an internet search on the Bill of Materials number, we figured out the axle was from a '93 or '94 Ford F350. Immediately after that, we found that the stock tie rod was mounted lower than our M-715's tie rod and the stock Ford part was bent to clear the differential cover. We were loathe to lose tie rod clearance, and with near 8,000 lbs of truck any bend or rock hit could lead to disaster real quick. The stock Ford knuckles don't have any provision for a high-steer setup, nor is there an easy was to bolt high steer arms to an OEM ball joint knuckle.	While the Ford axle does have...        read full caption While the Ford axle does have dual-piston calipers, the calipers are retained by two small pieces of spring steel at either end of the caliper. While we've not heard of any Super Duty owners talking about them backing out, but then we don't talk to many Super Duty owners. We'd rather our calipers be retained with bolts.	Both the tie rod location...        read full caption Both the tie rod location and caliper mount are cast into the Ford knuckle, so the only option was to swap knuckles. Since we only had one knuckle to begin with, we were in the knuckle market anyway. Dynatrac had the solution for us with high-mount steering arms, and bolt-on dual piston calipers. A friend with a lathe spun up a 1/2-inch thick adapter ring to mate our five-bolt Ford spindle to the six-bolt Dynatrac knuckle and it spaces the spindle and hub to the stock Ford distance from the ball joint.
We got one "automatic" hub...        read full caption We got one "automatic" hub with our used Dana 60 purchase and we knew we wanted to go with manual hubs. If we had all the 30-spline parts we'd have run them and upgraded later, but for a truck this big and heavy, we just couldn't justify spending money on 30-spline parts. Sure the outer shafts are a bit more money, but the lockout hubs are about the same price.	To get back up to the width...        read full caption To get back up to the width that we wanted, and use parts that no one else wants to keep costs down, we nabbed a set of dually hubs off eBay and we were able to sell the hub that came on the axle for what we paid for a pair of dually hubs. That brought us from 69 inches wide up to about 78 inches wide. The dually hubs and single rear wheel hubs use the same bearings and bearing spacing, so they will work on the same spindles, with the same axle shafts.	Once we had settled on the...        read full caption Once we had settled on the overall width for the front axle, we needed to figure out a way to get a rear axle in that same ballpark. Knocking on the door of 80-inch WMS to WMS doesn't leave any off-the-shelf junkyard jewels short of semi trucks. We went with a Dana 70HD out of an '87 dually Chevy pickup to get us in range of our 78-inch goal.
The dually Dana 70 hub and...        read full caption The dually Dana 70 hub and the GM Corporate 14-bolt hubs are interchangeable. Here you see the dually hub on the right and the single rear wheel 14-bolt hub on the left. By swapping the single rear wheel hub onto the dually Dana 70 we were able to go from the stock 73-inch width to 77 inches wide which is perfect to match our front axle.	Since this truck sees mud...        read full caption Since this truck sees mud frequently, we were itching to get rid of the stock four-wheel drum brakes. We can't begin to tell you how much it sucks to inspect/adjust/tear the drums down after every wheeling trip. So, we are going to put disc brakes on the rear in place of the stock drums. However, thanks to swapping hubs, we've got quite a distance to make up between the stock mounting flange and where the caliper needs to ride. We'll figure out where and how to place the caliper after the axle is in the truck.	With the same rotor, caliper,...        read full caption With the same rotor, caliper, and brake pads in all four corners, we've got enough spares on board to keep going if something goes wrong, and maintenance becomes a no-brainer. Besides, we've got a lot of truck to stop. These beefy 1-inch-thick brackets from Dynatrac are the stoutest we've seen and once the axle is mounted in the truck we will be able to figure out exactly where to mount the brackets.