Overland Vehicle Outfitters

Project Flatfender: Rear Axle

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Rear Axle
One of the big benefits of the 1970 Renegade chassis is that it came with the rear flanged Dana 44 axle.  I prefer the strength of the flanged axle shafts over the tapered two-piece shafts.  The stout differential housing and axle tubes have adequate strength and then some for my lightweight, fiberglass-bodied CJ with V6 power.  Remember that the Dana 44 rear axle has been used in many full-size trucks behind V8 engines over the years, and it's a step up in strength from the original Dana 41-2 rear axle that came in my '47 CJ-2A. 
 
I began my rear axle rebuild by disconnecting the rear spring shackles and then removing the u-bolts securing the axle to the springs.  Once the axle assembly was free, I set it on a bench where I could easily start the disassembly.  (At this point, I had already sandblasted the entire rolling chassis, so the outside of the assembly was clean.)  I removed the old drum brakes including the drums, shoes, hardware, and wheel brake cylinders.  All of these parts would need replaced, except a few pieces of the hardware that are non-wear items.  In the old days, it was common for mechanics to rebuild brake cylinders, and you can still get rebuild kits.  For me, however, it's worth the few extra dollars to simply replace the cylinders and not have to worry about inspecting the bores, etc. - we're talking about 40+ year old parts, and replacements are very reasonable.

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Once the brakes were removed down to the backing plates, I removed the diff cover and drained the gear oil.  It was pretty dirty, but there was no sign of water contamination or metal particles - both good signs.  After cleaning out the differential with brake cleaner, I found the rear ring and pinion gears to be in excellent shape with no chipped or broken teeth.  Since I'd be sticking with the 3.73:1 ratio, this would save me from buying a new ring and pinion set.
 
I unbolted the axle bearing retainers and removed the axle shafts, which were also in excellent condition.  After cleaning the grease off of the bearings, it's necessary to remove the retainer ring that holds the bearing in place on the shaft.  To do so, I drilled a 1/4" hole in the center of the retaining ring about 3/4 of the ring thickness deep, being careful not to drill all the way through to the axle.  I followed-up with a heavy hammer and a chisel, at the point where I just drilled the hole, to crack the retaining ring all the way through; a few good raps did the job.  Once the retainer was cracked, it slid off the axle shaft with very little effort.  I used a bearing separator and a couple of pry bars to gain enough leverage to work my way around and remove the old bearings and outer seals from the shafts.  With the axle shafts cleaned, it was a good time to replace the wheel studs and cover the axle flanges with a protective coating of black Rustoleum paint. 
 
Next I cleaned out all of the old caked-on grease from the ends of the axle tubes so I could clearly see the bearing races (cups).  I carefully removed these using an internal jaw puller, and also removed the inner axle seals.  Lastly, I did a final cleaning of the axle tube ends. 

 

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(Sidebar:  There were a couple of variations of the Dana 44 rear axle used by Jeep in CJs from this era.  One version did not employ an inner axle seal, and the axle bearings were lubricated by the gear oil from the center differential.  The downside to this design is that if you are, for instance, driving a trail with extended sidehills, the high-side bearings could potentially suffer from oil starvation and overheat.  The second version uses inner and outer axle seals and the bearings are packed with grease in the conventional manner.  This axle housing has a grease fitting near each axle tube end, allowing for easy addition of grease to the bearings.  My axle is the latter version; see the arrow in the picture above for the location of the grease fitting.  It's worth noting that the former can be converted to the latter, even without the grease fittings, by the addition of the inner axle seals and packing the bearings and bearing cavities with grease.)

 

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I then moved to the differential and removed the carrier and ring and pinion gears.  I've already covered the removal, installation, and gear setup procedure in relation to the front axle, so I won't spend time rehashing it here.  The experience with the rear was fairly unremarkable and the gear setup went smoothly and resulted in a nice pattern with all the measurements within spec.  A full installation kit and new LubeLocker gasket were employed as with the front.  
 
I decided to install a traction aiding differential in the rear as well.  The same needs and requirements applied to the rear as to the front, so I settled on an Auburn Gear Pro Series Limited Slip differential.  This limited-slip employs a cone-type clutch system that offers smooth and progressive engagement without 100% lockup, much like the Detroit Truetrac.  The differential comes in two flavors: the standard clutch pre-load and a more aggressive pre-load, which is what I installed.  Both come with hardened spider gears for durability and longevity under tough usage.  This differential also has no clutch packs to wear out, so there's no additional maintenance.  Together with the front Truetrac, this should be prove to be a very competent combination.  (In the picture above right, you can see the difference between the OEM carrier with open diff vs. the limited slip in the foreground.)

 

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With the hard part done, there were a few final details to attend to.  I sprayed the complete axle assembly with several coats of rust-resistant paint for a clean, refurbished look and protection from the elements.  As with the front axle, I replaced the original thin OEM differential cover with the much thicker version OEM diff cover.  This will help provide added protection from rocks and tree stumps.  And like the front axle, I removed the original axle vent (which is on the drivers' side axle tube rather than the center housing - see picture below left) and replaced it with a threaded barb that will accommodate a rubber vent hose and check valve.  Once done, the entire assembly was bolted back onto the springs with new u-bolts.

 

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E-mail us at:  rmiller@ovoonline.com

Overland Vehicle Outfitters
Marysville, OH 43040