Another reason for a front diff change

Jeepin Al · **Posted:** Tue Feb 28, 2006 8:58 pm

OK boys and girls,

I am just about to throw the towel in on the IFS on our KJ's. Thought you would never hear me say that. I will be getting my KJ back from the shop, OK 4WD in Stewartsville, NJ the only guys that I trust to fondle my baby, and the only guys that can put up with an over bearing pappa. They have discovered that the needle bearing on the right side of out KJ's has been replaced by MOPAR with a plastic bushing. It seems DC was having a lot of trouble with the right side of the front diff. Most of you have complained that side was very loose The axel would move up and down. Some blamed it on the CV joints.

Well I am here to say, it is the bearing the intermediate shaft is riding on. The needle bearing still sold by the dealers, even though the part number has been changed, had a bigger diameter than the shaft. It cause two seals and one shaft to go bad in my KJ just after 250 miles, (well around 20 of them were at Paragon). Now they replaced an oversized metal bearing (pi$$ poor engineering) with a plastic bushing with grooves in it so the oil could flow around the axle, thus allowing the shaft to ride on a bed of oil. They must be out of their minds...what happen to all those good german engineers!!!!

So I would expect that those with 2005-2006 models are now riding on plastic bushings.

Question is Why can't they get this right, its not rocket science? We aren't building a watch either, but the tolerences should be such that an axle rides on the bearing, not air or not one roller of the bearing group!

So in my best NJ Tony accent; wha's up wit that. These engineers types at da DC needa a wacken!

I hope DC is reading this board from time to time, so they can get an idea of how their product is performing. See now if we kept our KJ's to the mall parking lot none of this would have happen!

As usual, sorry to bore (boar) you to death, but I am sometimes a little long winded, or is it that I just need to break wind once in a while?

Al

Jeepin Al · **Posted:** Tue Feb 28, 2006 9:00 pm

Don't look now, that crazy jeepin al is on his soap box again!

PitViper · **Posted:** Tue Feb 28, 2006 9:20 pm

hmmmm I wounder why they didn't go with brass...

cheap son of a guns

RkyMtnKJ · **Posted:** Tue Feb 28, 2006 11:18 pm

wow this make me feel great about buying a brand new jeep :evil:

so whats the expected lifetime of this prastic part and what can i expect in the long run...sitting at 10xxx here and cranky after i heard that

Ed · **Posted:** Tue Feb 28, 2006 11:37 pm

Are there any solutions, like getting a replacement bearing that's the correct size for the shaft?

Is this only a problem with big lifts like your five-incher Al? Or is it game over for any IFS KJ lift above about 3.5" - maybe someone should tell Rocky Road this before they start making their high-angle drive shafts!

Jeepin Al · **Posted:** Wed Mar 01, 2006 12:32 pm

As always I do my best thinking while I sleep, dreaming about lift kits etc, (boy do I need a life) or while on the potty! I ordered a bearing from a local dealer so I knew it would be there for the shop. Instead of waitng for the shop to tear the thing apart, and than ordering the parts. The shop didn't hear from that dealer, went to another that had the new bushing in stock (strange ain't it). Well I am going to take this new bearing and size it. The best way to solve the problem with the older KJ's is to get the shaft sleeved to the size of the bearing, a simple procedure any machine shop should be able to do. I will keep everyone posted.

As for the bushing, based on my conversations with another dealer, and the shop, the plastic/?? material is harder than brass, and should last the life of the diff, (I take that as 100K). We will see. I asked about the other side, no real ans. Interesting. I think sometime this week I will call the DC hotline, where they don't tell you that much, but it never hurts.

Where is the old AMC? I called them all the time, actually spoke to either a service guy or an engineer, and they would talk with me for what seemed like hours about engineering and parts relative to the Jeep. Once I called about welding to the frame, to see if it was heat treated. I was on the phone for almost 45 mins. talking Jeeps with the guy. WE NEED CUSTOMER SERVICE LIKE THAT AGAIN! AMC was always ahead of their time.

As for the lift, mine will use your existing lift, and combine it with my set up, so you will not need to throw your Rusty's, Frankinlift, or whatever away. You will need new a-arms, I have developed a set that now drop 3 inches and hold the correct ball joint angle. You will just add my lift to yours. The CV joint angles will remain the same. My lift with out a 2.5 inch lift should net you around 2.5 inches, with no CV angle change over stock. You will need my a-arms however! :twisted:

I will be installing the lift with in the next couple of weeks, and my 33" tires should be in next week. Lets see how much damage I do!

Al

jdreckard · **Posted:** Wed Mar 01, 2006 12:54 pm

Is the bushing plastic or a composite (graphite) material? The new composite bushings when used in the proper applications will outlast any metal. They also can come with a lubricant impregnated in them to extend wear even further. Even some plastics have shown to wear better than metals. The plus there is shaft doesn't only the bushing and so you dont get the grooving associated with metal bushings. I'm not defending them only suggesting that there may be some sound engineering behind this that we dont know about. Of course it could also just be the bean counters taking over as they seem to be doing everywhere.

Ed · **Posted:** Wed Mar 01, 2006 7:09 pm

Quote:

As for the lift, mine will use your existing lift, and combine it with my set up, so you will not need to throw your Rusty's, Frankinlift, or whatever away. You will need new a-arms, I have developed a set that now drop 3 inches and hold the correct ball joint angle. You will just add my lift to yours. The CV joint angles will remain the same. My lift with out a 2.5 inch lift should net you around 2.5 inches, with no CV angle change over stock. You will need my a-arms however!

Al, you're a bloody legend!

Presumably you also don't need any special high-angle drive shafts if the CV angle doesn't change. How the heck does that work then? You get more lift, so the hub must be further away (vertically) from the diff than it was, and you're not dropping the whole cradle. So how? It's like magic!

There'll be new upper and lower a-arms, yes?
What about the rear?

I'm literally jiggling around with excitement!

PitViper · **Posted:** Wed Mar 01, 2006 7:36 pm

Al I remember you saying that you wanted to reach 5" of lift. So my question is will the 3 link rear handle that much lift without killing the ball over time?

Also I got my uppers today! now i'm waiting on frankenlift.

Jeepin Al · **Posted:** Wed Mar 01, 2006 7:53 pm

Well I am cheating a little, look up the post titled Lift experimentation or lift experiment and you can see my shade tree answer for the rear. I am working on a three link for the back.

The front, I am placing a spacer between the cradle and the unibody, I will need to work on the motor mounts but I think I have that figured out, ot I may just drop the entire drive train. Kinda defeats the lift if the entire drive train is dropped, but.......

more to come

Al

0311_DoC · **Posted:** Thu Mar 02, 2006 1:16 am

Cant wait to hear more bout this.......

QuietOutdoorsman · **Posted:** Thu Mar 02, 2006 11:06 am

Al,

As one of those engineer types (not for DC, I design airplanes) you've got my full attention on this bushing issue. Got some questions for you, and please let me know if I can be of any help.

Is the needle bearing press fit into the differential housing or is it bolt on? I honestly haven't spent the time under mine to know what that bearing looks like.

How much of a gap is showing between the bearing inner sleeve and the axle shaft? Is the inner sleeve being rounded out due to excessive axle travel? In other words, does dropping the wheel to full droop cause that bearing to bind up at all?

It would be best to have a net fit of the axle shaft to the bearing inner sleeve, but there are machining tolerances on everything....and KJ's aren't exactly a hand built machine.

As for the plastic replacement......carbon fiber could work, but I would be surprised if DC went that route. I would assume that it's a "plastic" along the lines of a high density poly-ethylene (HDPE), and for street use or light to moderate off-road use that would definitely work. HDPE makes for a very good wear surface and holds it's composition when soaked in oil. I should mention that my idea of "light to moderate off-road" does not include crawling at MOAB or Paragon!

Dirk

PitViper · **Posted:** Sat Apr 01, 2006 12:51 am

bump

Now my right front is making a clicking sound that changes with speed. (I can hear it most at 35-40mph) I remember hearing it before the lift but didn't think much of it. After the lift I really started to listen to all the noises my jeep makes, and now i'm worried I may have this bearing problem.

OzLtd · **Posted:** Thu Apr 06, 2006 1:00 am

My 05 built KJ CRD LTD is going in for its 1st oil change on Wednesday 12th. I'm going to ask them to inspect this bush to see what its like and what its made of.

Another reason for a front diff change

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