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Unread 11-01-2014, 12:15 AM   #1
evan1395
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Metal found in diff fluid?

So I took my ZJ into my mechanic who barely ever has to touch my rig, for him to drop the carrier and press off and on new carrier bearings that I supplied. He shoots me a text today saying he found metal shavings circulating throughout the entire axle housing and that it would be a good idea to swap out the pinion seals and bearings while he is at it.....for an extra $400 -.-
I cant afford that, I could barely afford the $350 diff carrier bearing job.
My question is, are metal shavings really THAT threatening to a pinions seal/bearing? The rumble I was getting in the rear end was clearly carrier bearings. It would get worse during corners, which from what I read, is a tell tale sign of bad carrier bearings on a C-Clip axle.
Shot pinion bearings are more of a squeak rather than a rumble? I have ZERO driveline vibrations.

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Unread 11-01-2014, 01:42 AM   #2
shaban
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I'd suggest not doing the pinion bearing/seal unless you have to, that involves re-setting the preload etc, not many mechanics can do it right.

Bad pinion bearing gives you a whine at about 50-80 mph, which changes when the axle is driving and coasting.

The only reason why you should be doing the pinion is either chunks (not shavings/flakes) of metal found in the oil, excessive leaks from the seal or noise/vibrations.

If it ait broke, dont fix it.
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Unread 11-01-2014, 01:51 AM   #3
evan1395
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Quote:
Originally Posted by shaban View Post
I'd suggest not doing the pinion bearing/seal unless you have to, that involves re-setting the preload etc, not many mechanics can do it right.

Bad pinion bearing gives you a whine at about 50-80 mph, which changes when the axle is driving and coasting.

The only reason why you should be doing the pinion is either chunks (not shavings/flakes) of metal found in the oil, excessive leaks from the seal or noise/vibrations.

If it ait broke, dont fix it.
Im kinda feeling the same way. The guy is usually pretty good about fixing and addressing the problem I bring to him, no questions asked. But this time he was REALLY pressing the matter of replacing the pinion seal and bearing. Why?! I have no idea. The rear end is smooth as butter with no leaks or vibes...just the pesky carrier bearing growl.
Shavings are normal in diff fluid, am I wrong?
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Unread 11-01-2014, 04:02 AM   #4
Timo_90xj
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Rear carrier bearings on my niner where bad, and rumbled. I pulled the carrier, unbolted yoke and checked pinion bearings - inner & outer bearing races and bearing rollers both were pitted fairly seriously. Only tiky metal flakes and silverish fluid came out, pinion had no play or leaks, couldn't hear a thing from it (possible the carrier bearing rumble masked it).

What I'm saying is, it might be a good idea to replace the pinion bearings now, instead of first doing the carrier, then finding out within couple rhousand miles you just ruined a good set of carrier bearings with worn pinion bearings, needing to buy a full rebuild kit and shim the axle again. Do it once and do it right the first time.

Edit: I would definitely at least check the pinion bearings when the carrier is out. Any mechanic with a dial- type torque wrench can setup pinion bearing preload with a new crush sleeve in under half hour. If not, he/ she shouldn't be doing carrier bearings either.
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Unread 11-01-2014, 05:09 AM   #5
shaban
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Well, there's a shim under the larger pinion bearing race that sets the pinion offset (sometimes there's just an oil baffle with no shim, selected by pinion offset number engraved on pinion head), and quite often it's getting destroyed when pulling the bearing.
So, at least he'd need a replacement shim/baffle of right thickness, and possibly re-check the gear contact after the assembly, and re-do it if necessary.

I'd not trust with that anyone but a good mechanic that mostly does diffs (rather than an all-rounder).
Carrier bearings are cheap and reasonably easy, pinion bearings - not so much and requires a fair bit more skill.

Again, talking about crush sleeve, a good half of the mechanics just rattle-gun the nut up and don't worry about that. It rarely shows straight away, and it's hard to blame them 10000 k's down the road.

PS: And as for $400, you can get a decent junkyard axle for about $150-200 that will likely last you another 50-100 thousands.
You can get them with changeover 1- or 3- months warranty too.
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Unread 11-01-2014, 07:06 AM   #6
Timo_90xj
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Quote:
Originally Posted by shaban View Post
Well, there's a shim under the larger pinion bearing race that sets the pinion offset (sometimes there's just an oil baffle with no shim, selected by pinion offset number engraved on pinion head), and quite often it's getting destroyed when pulling the bearing.
So, at least he'd need a replacement shim/baffle of right thickness, and possibly re-check the gear contact after the assembly, and re-do it if necessary.
You do NOT need to - never (!!!) - add or remove ANY shims on the pinion on a crush-sleeve axle when checking pinion bearings. If you pull the yoke, check the condition of the pinion bearings, and re-install with the same bearings, a new crush sleeve, new pinion seal and new yoke nut is all you need. Even on a shim- type preload, you can use the same shims for adjusting preload, or possibly replace one shim with a bit thicker one to compensate for bearing wear if they are otherwise good.

Only - and I mean only - if you replace pinion bearings, you need to shim the pinion to achieve correct pinion depth.


Quote:
I'd not trust with that anyone but a good mechanic that mostly does diffs (rather than an all-rounder).
Carrier bearings are cheap and reasonably easy, pinion bearings - not so much and requires a fair bit more skill.
R&P install is for some unknown reason thought as an almost impossible and somehow magical job - it's not. If you know what you're doing and take your time, any home mechanic can do a full R&P setup provided he/she has the right tool (case spreader is not necessary).

I've done a few R&P sets, and never had any issues with them (have put over 30k on one of the sets before I sold the vehicle). Pinion depth setup may require a few tries to get it right, but it's nothing impossible to do.


Quote:
Again, talking about crush sleeve, a good half of the mechanics just rattle-gun the nut up and don't worry about that. It rarely shows straight away, and it's hard to blame them 10000 k's down the road.
That may be true, but those are just shady mechanics who shouldn't even touch a diff cover, let alone axle bearings..
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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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Unread 11-01-2014, 07:38 AM   #7
shaban
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Timo_90xj Totally agree with what you've said.
About the shims - yes, I meant the shims may need replacement if changing the pinion bearings.
And yes, gear setup is not too difficult as such, just takes a lot of time and patience. DIY mechanic may have it all aplenty.

For a commercial mechanic time is money, that's why often they take shortcuts, that's what I'm worried about.
I guess that all comes down to how good you think your mechanic is.
I'd not expect an average mechanic do the pinion bearings and crush sleeve the proper way,
check the gear pattern and readjust as necessary, unless they've been doing diff work for living.

I did my front diff myself, 15'000K down everything's fine so far. But I guess not everyone's got time and tools for this.
Anyhow, I've had a few negative experiences with mechanics which sort of pushed me the DIY way.
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Unread 11-01-2014, 11:26 AM   #8
evan1395
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Here is what my mechanic said this morning.

" Good Morning Evan. Here is what I got. The pinion bearings appear to be intact. There is no looseness or excessive noise from that area while listening to it in the air. It is screaming from the left carrier area. With the cover off and the axles out, there is metal in both tubes. If it was my vehicle I would leave in the pinion and install the locker. If it needs shims I can look for them Monday. We need to clean the housing."

So im sticking with just the carrier bearings for now as planned.
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Unread 11-01-2014, 08:04 PM   #9
96zedjay
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My experience with axle/diffs is ANYTIME the carrier bearings get bad enough to make noise and need replacement they have
already released their payload of debris into the diff....So if the pinion bearings arn't gone now they are on there way out.
Bonehead move to just replace the carrier bearings. Do the pinion bearings now and be done with it or look at going back in the near future. And when the pinion bearings do crap out more than likely the carriers will get trashed again.
Just my experience over the last 40 years and 300+ diff jobs. Lot of the ones I get in " I don't understand it, I just had the carrier bearings replaced, the guy said the pinions were fine." The parts are cheap and the labor to do them all is not much more. most of the time is in pulling the cover, axles ect. It's an extra hour at best. $400 extra? does that come with dinner,flowers and KY jelly?
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Unread 11-02-2014, 03:58 PM   #10
evan1395
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Quote:
Originally Posted by 96zedjay View Post
My experience with axle/diffs is ANYTIME the carrier bearings get bad enough to make noise and need replacement they have
already released their payload of debris into the diff....So if the pinion bearings arn't gone now they are on there way out.
Bonehead move to just replace the carrier bearings. Do the pinion bearings now and be done with it or look at going back in the near future. And when the pinion bearings do crap out more than likely the carriers will get trashed again.
Just my experience over the last 40 years and 300+ diff jobs. Lot of the ones I get in " I don't understand it, I just had the carrier bearings replaced, the guy said the pinions were fine." The parts are cheap and the labor to do them all is not much more. most of the time is in pulling the cover, axles ect. It's an extra hour at best. $400 extra? does that come with dinner,flowers and KY jelly?
Cute.
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