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-   -   OEM Front Wheel Unit Bearing Study (http://www.jeepforum.com/forum/f96/oem-front-wheel-unit-bearing-study-1000223/)

ronjenx 03-27-2010 05:36 PM

OEM Front Wheel Unit Bearing Study
 
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.

http://i776.photobucket.com/albums/y...ubAssembly.jpg

http://i776.photobucket.com/albums/y...plodedView.jpg

http://i776.photobucket.com/albums/y...ngandRaces.jpg

http://i776.photobucket.com/albums/y...sinHousing.jpg

USAntigoon 03-27-2010 07:17 PM

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:

ronjenx 03-27-2010 07:45 PM

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.

Hellbound13 03-27-2010 09:59 PM

Quote:

Originally Posted by ronjenx (Post 9171728)
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.

Do you have a link of where to get the Timken bearings, and do they come with wheel studs?

ronjenx 03-27-2010 10:06 PM

Quote:

Originally Posted by Hellbound13 (Post 9172541)
Do you have a link of where to get the Timken bearings, and do they come with wheel studs?

No link. I learned about it last time I was at VIP. I think hubs usually come with the studs installed.

Hellbound13 03-27-2010 10:08 PM

Quote:

Originally Posted by ronjenx (Post 9172572)
No link. I learned about it last time I was at VIP. I think hubs usually come with the studs installed.

What is VIP?

ronjenx 03-27-2010 10:12 PM

Quote:

Originally Posted by Hellbound13 (Post 9172576)
What is VIP?

It's a parts store. I thought nation wide, but a site search revealed New England only.

The Timken hub is about $100, with a lifetime warranty.
If they are indeed tapered roller bearings, I would be tempted to get them when mine go out.

Hellbound13 03-27-2010 10:20 PM

Quote:

Originally Posted by ronjenx (Post 9172600)
It's a parts store. I thought nation wide, but a site search revealed New England only.

The Timken hub is about $100, with a lifetime warranty.
If they are indeed tapered roller bearings, I would be tempted to get them when mine go out.

Do they have a website I can order from or would someone else carry this bearing?

ronjenx 03-27-2010 10:26 PM

Quote:

Originally Posted by Hellbound13 (Post 9172633)
Do they have a website I can order from or would someone else carry this bearing?

www.vipauto.com/

You have to find the nearest store, and call them. I have not seen a way to look up parts on their site.

Hellbound13 03-27-2010 10:29 PM

Quote:

Originally Posted by ronjenx (Post 9172649)
www.vipauto.com/

You have to find the nearest store, and call them. I have not seen a way to look up parts on their site.

Thanks Ronjenx. Your posts are always very helpful!

Hussler 03-27-2010 10:32 PM

Man, hubs for my XJ only cost 74 dollars new. How much is it to repair them?

Prot 03-27-2010 10:41 PM

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.

ronjenx 03-27-2010 10:42 PM

Quote:

Originally Posted by hussler737 (Post 9172672)
Man, hubs for my XJ only cost 74 dollars new. How much is it to repair them?

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.

Hellbound13 03-27-2010 10:44 PM

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?

Hussler 03-27-2010 10:47 PM

Quote:

Originally Posted by Hellbound13 (Post 9172706)
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? :(


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