xj hub problems

Colin

Active Member
Joined
Sep 9, 2015
Location
Climax
so ive gone threw 3 brand new moog hub assemblies in the past couple months. replaced the first one right after i purchased the jeep and didnt think twice about it. took it to uwharrie alot before my surgery. after surgery i had time to kill and managed to slowly keep myself busy with replacing worn out stuff on the heep saw that my passenger side wheel had a lean to it, so up on the lift it whent the wheel bearing was bad of course it actually came off the jeep in two pieces ive never seen a hub assembly do that before. put a new one on and decided to drive it to my buddies house didnt make it 2 miles before turning around because of death wobble once again the wheel bearing was bad ,so ordered another replacement moog same as the last time. while it was on the lift i put a rugged ridge tie rod and drag link assembly on bc my rustys tie rod was bent and tres were worn slap out. decided to test out the new steering, i built my own pitbike track beside the house. so i took it over a couple of my jumps then drove it down my neighborhood to get the mud off, parked it in front of the shop and noticed the passenger tire leaning inward. i was like wtf, jacked up the tire and again the wheel bearings were loose. anyways does anyone know what could be causing this? im at a loss and dont feel like throwing away my money on hubs
 
175-180 sound right?
 
Colin said:
175-180 sound right?
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Yep

What size tire and wheel offset?

There are at least 3 different hubs ( different offset) over the years of XJ d30s, are you sure you have the right one? This would be a stretch, because if it's wrong, I think the caliper and rotor won't line up, stuff wouldn't fit right, it should be obvious something is wrong.
 
36-13.50 on 15x10 steel wheels everything fits like it should no hammers needed lol
 
You don't actually mention that the wheel bearings are all on the same corner, but I assume they're in the same corner?

I'd check to see if there is something wrong with the axle stub, maybe buy another axle stub. If there's something wrong with it then the axle nut may be bottoming out on the axle stub or something like that before the bearing assembly is properly preloaded. If the axle stub was stripped you'd likely have serious problems getting to full torque, so you'd know that.. If the Jeep had a decent amount of mileage when you bought it, and a wheel bearing went bad, it's possible that someone damaged something replacing a wheel bearing before you bought it.

Also, what are you doing when you torque the axle nut? Are you lowering the chassis back down to hold the tire/wheel stationary while torqueing it? If you're doing that, you may be putting too much load on the bearing before preload is applied, which can be a damaging thing to do to a bearing.

But, if you've over-torqued the bearing, that would kill it pretty fast as well. Probably not as fast as if you're totally lacking preload though, hard to say.

I don't think you're failing bearings because the bearings are bad, I think you're failing bearings because something is wrong with the other parts or with your assembly method.

Once you find out what's wrong, you could also try Timken or SKF units instead of Moog, especially if there is a tapered roller bearing unit available. I don't know why Moog bearings would have problems, they make really good suspension stuff but I've never used their bearings. Timken and SKF are all I try to buy usually.
 
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15x10's with a 36" tire is murder on dana 30 unit bearings, much worse if you have a negative offset wheel. I'm guessing you have a 3.75 or 4.5 inch backspacing wheel neither of which is a 0 or positive offset. Until you get rid of those wheels it's gonna keep happening.

What type steering do you run? is it still the factory style inverted Y? If so have you had an alignment done? Have you added lift to the front end without adjusting Toe-in? lifting the front suspension will increase toe-in the higher you go. You need to align the front wheels to almost no toe-in. If it is in fact toed in then the wheel bearings are going to be loaded anytime you're moving forward. 50 miles like that will destroy wheel bearings, throw in the terrible scrub radius of having those negative offset wheels and you've got a recipe for disaster.
 
MarsFab said:
15x10's with a 36" tire is murder on dana 30 unit bearings, much worse if you have a negative offset wheel. I'm guessing you have a 3.75 or 4.5 inch backspacing wheel neither of which is a 0 or positive offset. Until you get rid of those wheels it's gonna keep happening.

What type steering do you run? is it still the factory style inverted Y? If so have you had an alignment done? Have you added lift to the front end without adjusting Toe-in? lifting the front suspension will increase toe-in the higher you go. You need to align the front wheels to almost no toe-in. If it is in fact toed in then the wheel bearings are going to be loaded anytime you're moving forward. 50 miles like that will destroy wheel bearings, throw in the terrible scrub radius of having those negative offset wheels and you've got a recipe for disaster.
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Are the wheel bearings really that weak? I've heard of bearing problems with those but didn't know they were that sensitive.
 
The problem isn't that they're that weak it's where the load is applied. A truck with a true spindle that has outer and inner bearings has the load of the wheel centered between those two bearings. On a unit bearing the load is out past the end of the outer bearing. It's all about leverage. Hence the reason for having zero or positive offset wheels moving the load in towards the rotor. It's kinda like single shear vs double shear.
 
I understand the differences, but some unit bearings are much stronger than others. I'm surprised that a vehicle like that has fairly weak unit bearings, when a stronger design is readily available. Probably just costs less or was adapted from a lighter duty design.

The normal problem with unit bearings is that the bearings are closer together than a standard spindle design, so the effective bearing width (its a line of intersection based on width and preloaded contact angle) for angular contact bearings is narrower. Just that difference in width reduces the load capacity because it reduces the effects stiffness of the bearing assembly for a given load.

The greater moment from the difference in bearing location (what you're talking about) just makes the bearing width problem worse for the unit bearing.

Again though, why didn't they use a beefier unit bearing?
 
Lets just say there's a reason I hate all things jeep. Or should I say Chrysler. My ram has beefy unit bearings and they suck just as bad. Fords don't have near the problems.

They are plenty strong for the stock sized tires and wheels that they're designed for. Unfortunately we feel it necessary to use tires and wheels that are way beyond their capability of handling. Don't ever expect a profitable manufacturer to go above and beyond the minimum requirement for safety and longevity on a part that they can make even more money on replacing.

Instead of replacing them every couple months, spend that money on a wheel that fixes the problem right by bringing the centerline back in to lighten the load on the bearing.

If I had the time I'd find a machine shop to make me a couple hundred spindles that bolt into the unit bearing flange on the knuckle and uses oem 1/2 ton Chevy or ford hubs and rotors. As useless as that solution is over swapping whole axles I'd probably make millions off of it from guys that can't or don't want to pony up the coin to do an axle swap.
 
I think there are conversion kits that do what you're talking about. I can't remember where I've seen them. I think someone makes a 30 to 44 knuckle swap too.
 
Fabrik8 said:
I think there are conversion kits that do what you're talking about. I can't remember where I've seen them. I think someone makes a 30 to 44 knuckle swap too.
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Warn used to make a kit, but stopped production of it long ago.

As far as knuckle swaps, I've always wanted to try it myself. I was going to use explorer D35 knuckles. People argue the bearings are too close together and the slip on hubs suck, but at least they are serviceable and actually lock/unlock
 
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