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OEM Front Wheel Unit Bearing Study

28K views 43 replies 17 participants last post by  222Doc 
#1 · (Edited)
I have been wondering why the factory service manual says the front hub unit bearings are non-serviceable. The unit bearings in my old XJ were serviceable, and the JK's look a lot like them. I also wanted to know if my XJ rebuild tools would work on the JK hubs. They do.

I took an old JK hub apart, and this is what I found.
The hub is made by ILJIN, http://www.iljin.com/aboutus.htm
The spindle goes through the center of the bearings, and is swaged over on the inside. This makes a "hat", so the spindle cannot be pressed out until the hat is ground off, which destroys the spindle.
Another feature which makes the hub not serviceable is the bearing inner and outer races are not separate pieces as they were in the past. The spindle has been machined to serve as a race, and the hub housing has been machined to serve as two outer races. It's not a simple matter of pressing out the old bearings, and pressing in new ones. The entire hub and spindle must be replaced.

There was no sign of water intrusion, so the seals appear to be adequate.
There was very little grease in the bearings.
One race had 13 individual dents from 13 of the 18 balls. The spacing matched that of the balls. This indicates not a worn bearing, but a bearing that took a tremendous static shock load. It could have been the swaging process during manufacture, or, from an accident.
On the plus side, the JK ball bearings are bigger than the tapered roller bearings of the XJ hub.

My next step is to perform hardness tests on the races and compare them to the conventional Timken races in the XJ hub.
I will update this post when I do the tests.







 
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#2 ·
This is a real example of "Value Engineering" to cut out cost and weight ..End result is something which will work as long as you don't abuse it..Tapered bearings are way much better..They can carry much more load (shock loads, radial and axial loads as well) .

With ball bearing you have a stress raiser because the line contact between the ball bearing and the race is a much smaller and they are more vulnerable for extreme axial loads. I assume they did do a local induction hardening of the races(grooves). Just look for some discolorations in that area...If not they have used some High Alloyed steel instead..

Furthermore, there is NO adjustment of the bearings at all.. This is fully determined during the swaging process. This process is a fixed swaging load and will NOT compensate for tolerance stack-up..Result is a non consistent Quality product.. some will have too much preload (roller and race damages) other will have slight endplay.(early wear out)..
etc..

Indeed this is a unitized non serviceable unit..Typical of cars but NOT typical for off road units..Another Daimler Engineering intervention...

ronjenx Very good feedback.. well done with the pics...:thumbsup:
 
#3 ·
I was going to reserve judgment until I get the hardness test done. People are seeing early failure on these, though.

Thanks for the added detail. There is evidence of heat treatment in the area of all the races. My plan is to compare hardness of the races with that of the areas away from the races.

The old XJ hubs had tapered rollers. However, they lasted only 30K on the right, and 60K, on the left. The bearings were made in Japan. I replaced them with Timken bearings, (the hubs were rebuildable), which were still good when I sold the XJ at 186K.

Timken makes a replacement hub for the JK, available at VIP. I believe they are made the same way as the ones in this post, but with tapered rollers instead. It may take an e-mail to them to verify this.
 
#11 ·
Man, hubs for my XJ only cost 74 dollars new. How much is it to repair them?
 
#13 ·
Back when I rebuilt mine, they were expensive enough to make it worth it.
When my first one went out, for the price to have the dealer replace two, I was able to buy a 20 ton press, the tools to disassemble (and reassemble) the hub, seals, and a set of new Timken bearings.
 
#12 ·
Imagine that. Further evidence the JK is made out of crap in the cheapest way possible. Very good posts with very good information. I knew I was not wrong in my assesment that although the JK's overall design is very good, it is executed so cheaply that it ruins the potential greatness this generation could have had.
 
#14 ·
So it all started with, "man this steering shaft is junk" we need to fix that. Got a new one. Wait...I still have shimmy, man this tie rod and the ends are junk. Hmm wobble over potholes. These ball joints have play already? Need better ball joints. My steering is loose now! Oh great the steering box has lateral play!

Now its wheel bearings. Is there anything on these JKs that are built to last over 50K?
 
#15 ·
So it all started with, "man this steering shaft is junk" we need to fix that. Got a new one. Wait...I still have shimmy, man this tie rod and the ends are junk. Hmm wobble over potholes. These ball joints have play already? Need better ball joints. My steering is loose now! Oh great the steering box has lateral play!

Now its wheel bearings. Is there anything on these JKs that are built to last over 50K?
Don't say that, what are my kids going to wheel then? :(
 
#22 ·
We'll all get pissed off and get rid of our JKs, and JK'ers who don't get on forums will still be enjoying the best choice out there.
:laugh: Well, at least you guys still have that lifetime D/T warrenty going for ya, right?
 
#27 ·
Well maybe things will be better under Fiat and the new Penta star.
Good luck to y'all. :wave:
 
#29 ·
What gets me is my YJ was not like this. When something broke or wore out, I would fix it and it was done. Everything had a more solid feel to it. Yes my YJ had many deficiencies, but it at least felt like it was built to last. I like the greater towing capacity and more cargo room the JK has and the overall design. It is just when it came time to build it the cost cutting measures were excessive. Every time I have to bring my JK in to get something fixed, I have to rent a car which is always less than one or two years old. Even when I rent a cheap vehicle, it seems constructed out of better materials than my Jeep.

I never drove a TJ. I did enjoy my YJ. I recently almost trade the JK for an H2 or a corvette because of a braking problem that the dealer could not fix despite bringing it back multiple times in a five month period. I opened a case with corporate and I think the brakes are fixed now.

If this were my first Jeep, I would say it's a jeep, what do you expect, but it is not. The thing is, when it works right, it is awesome. The problem is, there are few days that it is not problematic. On those days it is truly awful. On Monday I have an appointment to replace several things under warranty which should help it.

I bought it July 2007. The only warranty it had was 3 years 36,000 miles. Even if stuff was covered under warranty, it does not help in the long term to replace one piece if crap with another piece if crap.

I am beginning to think that if I wanted a new Jeep in 2007 it would have been better and cheaper to build one from scratch out if aftermarket catalogs.
 
#30 ·
What gets me is my YJ was not like this. When something broke or wore out, I would fix it and it was done. Everything had a more solid feel to it. Yes my YJ had many deficiencies, but it at least felt like it was built to last. I like the greater towing capacity and more cargo room the JK has and the overall design. It is just when it came time to build it the cost cutting measures were excessive. Every time I have to bring my JK in to get something fixed, I have to rent a car which is always less than one or two years old. Even when I rent a cheap vehicle, it seems constructed out of better materials than my Jeep.

I never drove a TJ. I did enjoy my YJ. I recently almost trade the JK for an H2 or a corvette because of a braking problem that the dealer could not fix despite bringing it back multiple times in a five month period. I opened a case with corporate and I think the brakes are fixed now.

If this were my first Jeep, I would say it's a jeep, what do you expect, but it is not. The thing is, when it works right, it is awesome. The problem is, there are few days that it is not problematic. On those days it is truly awful. On Monday I have an appointment to replace several things under warranty which should help it.

I bought it July 2007. The only warranty it had was 3 years 36,000 miles. Even if stuff was covered under warranty, it does not help in the long term to replace one piece if crap with another piece if crap.

I am beginning to think that if I wanted a new Jeep in 2007 it would have been better and cheaper to build one from scratch out if aftermarket catalogs.
I know what you mean...

My Dad's XJ, and my previous TJ both felt more substantial...the TJ never gave me any problems...the XJ has had two issues in 11 years, and its still going strong...

My friend has a 2003 TJ Sahara, and I love the engineering of the JK over his TJ, but his seems so much better put together than my JK....

There is a guy on this board that drives a TJ, named Grogie, and he and I used to be on a different forum at the same time, and I kind of questioned why he got one of the last new TJ models with the JK coming out, and I kind of feel dumb for asking him that now...I kind of think he made the right choice...as I have said here and other places...I am keeping my JK until its dead and I hope that is at least 20 more years, but I am sure having to replace and redo a lot of inferior things...:(
 
#31 ·
I bought my 2010 Sahara Unlimited in January. I kept my 2001 TJ which is the strip model with the 4Cyl engine (of course it's been extensively modded). There is no question that the JK has some superior engineering updates. It feels solid and rides much nicer. As someone who has been under the TJ extensively.. (and i have replaced my non-servicable Timken bearing units in the TJ as well...) the JK may have some crap parts in there (so did the TJ) but the engineering updates are noticable and greatly improved.

That being said...i drove my TJ around town yesterday for the first time in almost two months...and it feels like driving a tractor or a go-kart in comparison to the JK. I absolutely LOVED it. I'm keeping BOTH!!!
 
#32 ·
It would be nice to learn more about the VIP hubs.
I see Quadratec has OEM hubs for $125 with a 12mo/12000 mile warranty. if we could get an upgraded version for less money, that would be bonus!

I've been suspecting my right side unit bearing recently. On a straight or a left-hand curve, there seems to be a growl from the front end.
On a right-hand curve, the growl goes away until I straighten out again.
 
#34 ·
Update (belated):

The hub Timken sells for the JK is made by ILJIN, the same as the OEM hub.
Several e-mails to Timken asking why they make tapered roller bearing hubs for other vehicles, went unanswered.

The good thing is it has a lifetime warranty, and is under $100.
 
#36 ·

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#37 ·
Changed my unit bearings this weekend and thought I would post what I used.
These are Moog parts that appear to be the same Iljin parts that all other suppliers including the original equipment are branding as their own. I got them through Amazon for $76 each >

Ronjenx, Please confirm that they are the same as you have seen. :tea:
That is the same as I have seen. As far as I know, Iljin is the only company making the unit bearing for the JK.
 
#40 ·
Hellbound13 said:
Do you have a link of where to get the Timken bearings, and do they come with wheel studs?
I got my Timken bearings from RockAuto
 
#43 ·
When I started this thread, I was disappointed the front hubs had ball bearings in them rather than tapered roller bearings, and in the fact the hubs are not rebuildable.

Well, my original hubs now have 262,000 miles on them, and are still going strong.
 
#44 ·
I just replaced one on the JKR so far. at 40k this year. Ball joints went at 20k. I bought two but the other is still ok. 37s hard trails is all it does. simple to fix. broke other things that cost much more. Jeep really only see trail miles many years now. So even if they only get a few thousand miles, that is a lot of trails miles. I would say these last longer then the 3.6......talk about design issues.....
 
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