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ZJ front axle swap or rebuild

Old 10-09-2016, 12:25 PM
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Default ZJ front axle swap or rebuild

First thing that I just want to put out there for anyone that finds this in the future. Rebuilding differentials takes precision and skill. You cant just slap parts in them like replacing brake pads.

I bought a 1997 ZJ last month and have been going through everything one piece at a time. It looks like the guy re-geared his own axles and did a pretty bad job of it. I already had to do an 8.8 swap in the rear, and now I have opened the front differential and glitter poured out. The gears honestly do not look too bad, but it looks like it ate itself once and was rebuilt. I was hoping for just a fluid change, but it looks like a complete rebuild is needed. Also the front CV shafts/hubs and the lower ball joints are due for a replacement.

So now my question is what to do? Should I rebuild the Dana 30 with quality parts, or should I do yet another swap? I am not a hard core off-roader, but I don't want to spend a bunch of cash rebuilding a 30 if I could upgrade for a reasonable difference in price. A 1 ton conversion seems like overkill, but dumping $1000 on rebuilding dana-30 does not seem too appealing.

Thoughts?

Best bang for the buck parts recommendations?
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Old 10-09-2016, 07:41 PM
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Quick-checking Summit Racing shows you can get a quality complete rebuild kit and a ring & pinion gearset for about $400.
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Old 10-09-2016, 09:06 PM
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Originally Posted by dave1123 View Post
Quick-checking Summit Racing shows you can get a quality complete rebuild kit and a ring & pinion gearset for about $400.
I did see the summit kit, but I do not know how all of the different kits compare. I would assume that summit would have some better than china stuff, but you never know.

I guess my simplified question is, I need to replace the shafts, ball joints, hubs, gears and rebuild the differential. About the only part that is staying would be the housing, steering knuckls and the carrier because it has an OX locker. If I am going to do all of that work, is rebuilding the Dana 30 my best option?
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Old 10-09-2016, 09:32 PM
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I have 4.56 gears in it now, and I cannot find that on summit. I find a bunch of kits for dana 30, but I do not think that they are correct because as soon as I enter 1997 grand cherokee as a filter, it removes everything but the 3.55 ans 3.73 kits from the search results.

I looked and mine looks like the stock low pinion dana 30, but I did not count the pinion or axle splines. The guy I bought the jeep from added a lot of upgrades, and he did not mention changing the axle shaft size or the front drive shaft.
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Old 10-10-2016, 12:16 AM
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Try Quadratec or Morris for your gears. The OX locker replaces the entire carrier assembly anyway. All you'll need there is bearings and shims. AND the bearings, shims, seal, and crush sleeve for the pinion. My 97 had u-joint axles in it. I'm aware you have a 5.2 and 249, but that shouldn't matter. U-joints are much easier to replace if you break one.

Last edited by dave1123; 10-10-2016 at 12:57 AM.
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Old 10-10-2016, 09:27 AM
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Originally Posted by dave1123 View Post
Try Quadratec or Morris for your gears. The OX locker replaces the entire carrier assembly anyway. All you'll need there is bearings and shims. AND the bearings, shims, seal, and crush sleeve for the pinion. My 97 had u-joint axles in it. I'm aware you have a 5.2 and 249, but that shouldn't matter. U-joints are much easier to replace if you break one.
It looked like a CV joint on there to me. It has a boot on it, and the passenger one is torn so I know that they are not going to last long. I did not peel the boot back though, I just assumed that it was a standard CV joint.

The gears have me worried though. They look fine and I cannot see any damage on them, but the amount of metal that came out of the oil is very concerning. I can see that the oil slinger is chewed up a little, and there is impingement damage all around the internal of the diff that lines up with the ring gear. It looks like the ring gear blew up previously? Not sure, but the dents that are in the OX locker cover have been ground down with a dremel tool at some point so that the cover would fit flush. Either it blew up previously, and the guy did a back yard rebuild re-using the oil slingers, or something is out of wack and eating the oil slingers and spitting out a bunch of metal filings. The gears are not noisy and dont sound too bad, so maybe it was just some metal that is being flushed out from the previous damage, but either way I dont want to get in there and replace the bearings just to have the ring and pinion fail in a couple months.
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Old 10-10-2016, 10:39 AM
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No, you have CV joints in the front axle. That's what's normal for a 5.2 with the 249. I'm just saying you can replace the axles with u-joint axles if you want. Replacing a u-joint is cheaper and easier than replacing the whole axle if a CV goes bad. After you get the diff apart, you can inspect the ring and pinion for damage, especially the pinion shaft if the bearings are toast.
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Old 10-10-2016, 11:18 AM
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Why in the heck are XJ stock axles so expensive? Just to make sure I have this right, 95 and newer XJ axles have the larger stronger U-joint and will swap right onto a ZJ. But the catch is that they are $220 each where the ZJ axles are $80 for the OEM CV. Blows my mind that they are that expensive. What would be the best axle to put in there regarding overall strength, excluding the chromoly shafts? Those just are not in the budget, but I assume that there are some different options that are better than the stock axle but at a reasonable increase in cost. Is there a 3 to 1 cost to benefit for swapping to the XJ axles?

The ring and pinion look fine, and the wear pattern on the drive side looks centered and okay. I do not think that any of the bearings are lunched, but might be on their way out. It is running quiet and smooth all things considered. My only real problem here was that it looked like 50% oil 50% glitter when I pulled the cover, and I could see that at some point there was a violent enough blow out to smash 1/8th inch deep divots into the CNC billet cover of the OX locker. It must be older, but I just do not see where that much metal could have come from to dirty up the oil that badly.

I can rebuild differentials and have done it in the past, but it is a pain in the *** and is expensive to do it right, so I only want to do it once.
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Old 10-10-2016, 09:09 PM
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I can only think of 2 scenarios why the cover is dented. Either the previous ring gear shattered or the locker came from one that did.



you could use 4.0 front u-joint axles, but pumping a 5.2 thru them, I would suggest you bite the bullet and use the XJ axles, especially with a locker.

Last edited by dave1123; 10-10-2016 at 09:12 PM.
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Old 10-11-2016, 08:55 AM
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Originally Posted by dave1123 View Post
I can only think of 2 scenarios why the cover is dented. Either the previous ring gear shattered or the locker came from one that did.



you could use 4.0 front u-joint axles, but pumping a 5.2 thru them, I would suggest you bite the bullet and use the XJ axles, especially with a locker.
So the XJ u-joint axles are 3X stronger or better than the stock CV shafts? That is my main question. It appears that the CV shafts in my jeep are original with about 130k on them. I could buy 3 sets of those for the cost of built U-joint axles. I could buy 6 sets for the cost of chromoly shafts, so for my uses it just does not make sense.

I guess that kinda answers my question. Replacing a half shaft is easy, and I would say easier than pulling and rebuilding a u-joint. Now I just need to decide whether I should take a chance and re-use the gears that are in there, or buy new gears.They probably will be fine if I really take my time to line up the pattern and set the backlash correctly.

Thanks for all the advice guys.
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Old 10-12-2016, 09:06 AM
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Speaking from experience with your set up if you have tires bigger than stock I would upgrade to the xj shafts. If it's an option for you check out your local salvage yard the shafts are usually less than $50, you may even be able to get the whole front axle for pretty cheap and be able to use your gears and locker. Plus from the xj it is high pinion so you will get the extra ground clearance and less angle on your front driveshaft
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Old 10-12-2016, 11:58 PM
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Originally Posted by JY95ZJ View Post
Speaking from experience with your set up if you have tires bigger than stock I would upgrade to the xj shafts. If it's an option for you check out your local salvage yard the shafts are usually less than $50, you may even be able to get the whole front axle for pretty cheap and be able to use your gears and locker. Plus from the xj it is high pinion so you will get the extra ground clearance and less angle on your front driveshaft
What years of XJ should I hunt for? I will probably have to call around to find one because pretty much all the jeeps here go to the Jeeps Unlimited junk yard and their prices suck really bad. I am talking $75 for a used valve cover and $350 for a okay condition rear seat in a YJ bad. On their website it looks like $950 for a complete dana 30 from a XJ. Either way, I bet they get 99% of the jeeps in the area and the normal salvage yards with normal prices are pretty picked over.
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Old 10-13-2016, 12:33 PM
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All xj front axles will bolt up no mods needed. Man I'm super lucky to have the salvage yard here their prices are amazing I got my jeep, motor, tcase, lift,well basically built the whole thing super cheap minus wheels and tires and a few other smalls. Lucked out on most of the parts but that's how it goes. I have a small build thread on here from when I still had it JY95ZJDD. Good luck man hope you find what you need
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