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Old May 1st, 2012, 10:24 PM   #1
tmhd2
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Default D44a pinion bearings question

I'll start this off by saying I'm not an expert with axles by any means...

The patient is a 96 ZJ V8, which has the 'lovely' aluminum D44 rear end. Jeep has 180k miles on it, and somebody has obviously been into this axle before (more on that in a minute).

I bought this Jeep over the winter with a completely shot D30 front. The axle made so much noise that I totally missed the noises from the rear. I first noticed it as I got off the highway. As I slowed down, a cyclic 'grating / grumbling' noise was present. I noticed as I drove around town that the noise is most loud around 40ish MPH. My typical experience with axle noise is that bad pinion bearings will be impacted by acceleration / deceleration whereas wheel or carrier bearings will make a constant noise.

Armed with this belief, I put the Jeep on stands, ran it up to 40 MPH, and noticed the noise most prevalent around the driver's side wheel. I pulled the axles, did both wheel bearings for good measure (didn't get a chance to really judge their condition due to the slide hammer rendering them useless during the removal process), put it back together and noticed that it was just as loud as ever. Killer.

Pulled it apart again, pulled the axles, and pulled the carrier out. Nice, tight Timken branded bearing on the passenger side. Driver's side bearing has no markings on it, and slid right off the carrier (at least I only have to press one off now, right? lol). This bearing is also very worn and noisy when turned by hand.

Thinking this must positively be the culprit, I did a little victory dance and got to work with a bearing splitter and a hammer on the good side (might as well do them both, right?)

In the meantime, it seemed like the prudent thing to do to check the pinion bearings over thoroughly, as they are really all that is left in the diff at this point. I dropped the rear driveshaft, and lo and behold... The pinion turns nice and easy with no play or seal leaks or anything else out of the ordinary but it makes noise just like what i'm hearing when i drive. There are no rough spots or what I would consider an excessive amount of force to turn it...

The teeth on the ring and pinion show even wear, with no evidence of chipped teeth, etc.

Coming back to the first sentence in my post - I'm a bit out of my element, so here come the questions to the experts:

Is it normal to have some rotational noise in a D44a pinion? I'm guessing no, but hoping yes...

In the event that it is not normal, how serious of a problem is this? Keep in mind that there is no discernible play, leaking seal, typical accel / decel noise that accompanies failing pinion bearings. I would love to delay a total rebuild on this axle for at least a few months, but want to be realistic about the likeliness that this Jeep is going to SLSD this summer.

In the event that this is serious, would anybody in the Metro Detroit area be willing to charge a fair price to get it straightened out for me? I can either slap it back together and bring it to you, or you can come here and have the dis assembly already done for you. I can help or get the hell out of the way.

Thanks in advance

Tom
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Old May 1st, 2012, 11:47 PM   #2
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im pretty sure that since you removed the carrier bearings, your going to have to reset the gears. you cant just slap it back in there and role. tolerences are in the thousandth. at this point, you might as well replace the carrier bearings as well.
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Old May 2nd, 2012, 10:30 AM   #3
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I was under the impression that you could remove and reinstall the carrier without causing issues with the setup, as long as you put the shims and caps and everything back exactly where they came from. If I'm wrong, I guess I'm already up a creek...
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Old May 3rd, 2012, 07:32 AM   #4
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your carrier bearing should not just slide off the carrier like that. Either the bearing is very warn or the carrier is. It's usually the carrier that will need to be replaced. The bearings are harder then the carrier.

Check to see if a new bearing will slide on, or if is tight. The bearings are normally are machined more accuracy than the carrier and thus shims to account for the carrier, not the bearings. Thats why people use setup bearings to test shims and then install the new bearings and the setup is correct. The bearings can be swapped all day long as long as the shims are in the same location.

About your noise, It's hard to say if it's the pinion or not. Normal warn bearings will have slop or a sticky spot on the bearings when you turn. Is also hard to tell with the seal on because that holds the yoke also. I would pull the seal and check the bearing without a seal to see if its free and smooth. If it is, check the carrier to make sure the side that the bearing came off by hand is not warn. Press new bearings on it and put it back together to give it a shot. If it still doesn't work, then you will just need to change pinion bearings and see. You are not really out anything but time and some gear lube.
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Old May 3rd, 2012, 07:58 AM   #5
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Listen to Dylan. He knows what he is talking about by the sounds of things. Dont listen to that other guy. You know more than him already lol. Good luck and try to not over tighten the pinion nut when reinstalling it.
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Old May 3rd, 2012, 09:29 AM   #6
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Thanks for the advice Dylan!

I put it back together with new carrier bearings last night. I tried a trick that I saw online where you freeze the carrier and heat the bearings up in oil. It went right together with a few well placed taps from the dead blow hammer!

I still have one loose side, where I was able to install / remove the bearing by hand, but it is not loose enough to slip when the carrier turns (no evidence of it having slipped before either).

The diff is overall much quieter than it was before. It still has a grating noise that must be from the pinion bearings (matches the noise i heard when turning the pinion with the carrier removed) that can be heard around town. faintly. with the radio off and the windows up.

I think I'm going to keep and eye on the pinion and run it until something changes for the worst. When it does, I'll 8.8 it. I don't feel that dumping another dime into the 44a is money well spent. For now, he gears looked good, the carrier and outer / wheel bearings are brand new, there was not a noticeable amount of metal in the fluid when I initially drained it... Only issue is the slight noise from the pinion, which is still nice and tight.
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Old May 3rd, 2012, 09:32 AM   #7
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Does this sound like a good plan, or is it a ticking time bomb that is likely to explode at any second?

Not to be facetious, but I had a D35 pinion bearing howling for over 20k miles on one of my other Jeeps (when I was younger and less inclined to fix stuff before it broke). I don't know if I was young, dumb, and lucky or if this can safely be back-burnered.

Thanks again!
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Old May 3rd, 2012, 09:55 AM   #8
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I think I would run what you got for now.
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