Rear Pinion Bearing Going...

[Dalmus]

Took '03 XLS in to have my noisy rear end looked at, and after driving it around, the mechanic put it on the lift, went to the rear diff, and found there was a bit of slop in the pinion bearing.

He said that if I wanted to replace the outer bearing, I might as well replace the inner bearing as well since everything will be open. But he said that its often a bear to get the thing apart, and if something goes wrong and he has to force it apart, he might damage a shaft which would then put me in for all the gears, too... Not to mention it would be rather expensive, even though he does my work on the side. He was talking somewhere between 800 and 1200, spending on what the parts cost and how long it took him to do it (he said from experience on a couple Jeeps, its a good portion of a Saturday).

My question is, why even risk damaging anything... Wouldn't I be better off monetarily if I just got a rebuilt differential and did a complete swap? That way I don't have to worry about any damage in the disassembly of the bearings. In theory, it should be less labor time, too, right? I think I would also get the bonus of having the faulty ABS sensor in the diff replaced in the deal.

I have 150,000 miles on her now. She's in otherwise decent condition... Good pep, good body. I'd like to see her to 200,000, but I don't want to throw money away, either.

Thoughts? What would be a good source for a rebuilt diff? What about taking my chances with a "used" diff?

Thanks!

 

[imp]

Unless it is locked up due to broken parts within (which obviously yours is not), a properly disassembled center section requires no forcing apart, it literally falls apart, as ring gear bearing caps are loosened and removed, then the pinion gear itself is removed through the back of the case. It's rear bearing comes out with the pinion itself, while the front bearing falls out of the front by itself. One or both of those pinion bearings are shot, if the pinion snout (U-joint) flange can be moved any amount sidewise.

One unlikely possibility is that the pinion nut may have loosened in service, allowing the pinion to "slop" around, causing misalignment of the gear teeth, and accompanying noise. If this were the case, it is possible to retighten the nut using loctite, making certain the pinion bearing preload can be dialed back in. The loose nut scenerio should obviously be checked first, as properly tightening it just might solve the noise issue. imp

 

[Dalmus]

Unless it is locked up due to broken parts within (which obviously yours is not), a properly disassembled center section requires no forcing apart, it literally falls apart, as ring gear bearing caps are loosened and removed, then the pinion gear itself is removed through the back of the case. It's rear bearing comes out with the pinion itself, while the front bearing falls out of the front by itself. One or both of those pinion bearings are shot, if the pinion snout (U-joint) flange can be moved any amount sidewise.

One unlikely possibility is that the pinion nut may have loosened in service, allowing the pinion to "slop" around, causing misalignment of the gear teeth, and accompanying noise. If this were the case, it is possible to retighten the nut using loctite, making certain the pinion bearing preload can be dialed back in. The loose nut scenerio should obviously be checked first, as properly tightening it just might solve the noise issue. imp

That's not as unlikely as you might think. About four months ago, I had the front and rear pinion seals replaced. This would require the removal of the nut, correct? Maybe it was not properly tightened in the first place? I started noticing the noises from the rear end about about two months after that.

 

[Exproblems]

That's not as unlikely as you might think. About four months ago, I had the front and rear pinion seals replaced. This would require the removal of the nut, correct? Maybe it was not properly tightened in the first place? I started noticing the noises from the rear end about about two months after that.

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You are making me nervous! I just had my mechanic change a leaking rear diff pinion seal yesterday. I hope he tightened the pinion nut to proper specs and I had no rear diff noises prior to this work being done. Just the seal started to leak a little. I'll have to keep an eye on it I guess. Good luck with that rear diff issue.

 

[matt0248]

There are places that sell rebuilt diff's for these. Then it becomes just a remove and replace the diff job. Saves a lot of time. Do you have a limited slip or open differential? If limited slip after 150k the clutch packs may be worn out too, so if you are going to replace the pinion bearings then you may as well replace the clutch packs. And if you are going to replace the clutch packs ......Do you see where I am going with this? My pinion bearings were very noisy, when the shop took the drain plug out there was metal shavings and bearing material on the magnet. It got rebuilt and I was told the pinion bearings were trashed, clutch packs were trashed, and carrier bearings were trashed. This was at 75k miles.

 

[Dalmus]

There are places that sell rebuilt diff's for these. Then it becomes just a remove and replace the diff job. Saves a lot of time. Do you have a limited slip or open differential? If limited slip after 150k the clutch packs may be worn out too, so if you are going to replace the pinion bearings then you may as well replace the clutch packs. And if you are going to replace the clutch packs ......Do you see where I am going with this? My pinion bearings were very noisy, when the shop took the drain plug out there was metal shavings and bearing material on the magnet. It got rebuilt and I was told the pinion bearings were trashed, clutch packs were trashed, and carrier bearings were trashed. This was at 75k miles.

I have the 3.73L. The clutch packs were replaced at about 65K along with the bearings by the dealer under warranty (I got my money's worth out of that used car warranty!). I saw the itemized bill, would have cost be $2,400.

I'm agreeing with you... I think for the money it would cost to just do the bearings, why not just do the entire diff? Then I have new/rebuilt everything.

I'm seeing entire axle assemblies going for roughly the same price... it looks like that would be even less labor involved than replacing the diff. If I'm looking right, I'd have to pop the wheel assemblies, loosen a few bolts on the drive shaft, axel and diff, drop it, plop the other one in, and go in reverse. Seems like it would be a bit easier than pulling the axle out of the diff?

 

[imp]

Over and over, and yet ONCE AGAIN: Removing the pinion nut to replace the seal is a simple-seeming process. BUT, re-tightening it IS NOT! The nut as it is tightened, compresses a thin-walled SLEEVE located between the 2 pinion bearings. This establishes the correct PINION BEARING PRELOAD, by causing the nut to be VERY TIGHT, as it compresses the SLEEVE (called a "crush washer"). If the crush washer is not replaced as part of the nut removal process, proper bearing preload MAY BE REACHED before the nut is adequately tight.

At that point, the "mechanic" may: 1. Tighten it more, subjecting the bearings to excessive preload, and therefore early bearing failure,

2. Leave the nut insufficiently tight, and hope it does not loosen in service. Expecting this scenerio, experience should have caused him to slather the threads with Loc-Tite,

3. (CORRECT PROCEDURE): Remove the nut, washer (if present), U-joint flange or yoke, oil slinger washer, front pinion bearing. The crush washer then will be visible, and MIGHT be removable by sliding it off the pinion snout. New crush washer installed, reverse assembly process. Insurance? Replace nut with new, "prevailing torque type" (self-locking), use Loc-Tite if desired. Tighten nut until preload is within specs. That will take well over 100 ft.lbs. applied to the nut. It WILL NOT loosen in sevice then.

Lots of words here, sure. But it covers most of the novice-type questions and uncertainties. Surely, there are many mechanics replacing leaky pinion seals who do not yet understand the dual-function of that nut. I truly feel sorry for you several who have had bearings fail after a "simple" seal replacement job. imp

 

[Dalmus]

Over and over, and yet ONCE AGAIN: Removing the pinion nut to replace the seal is a simple-seeming process. BUT, re-tightening it IS NOT! The nut as it is tightened, compresses a thin-walled SLEEVE located between the 2 pinion bearings. This establishes the correct PINION BEARING PRELOAD, by causing the nut to be VERY TIGHT, as it compresses the SLEEVE (called a "crush washer"). If the crush washer is not replaced as part of the nut removal process, proper bearing preload MAY BE REACHED before the nut is adequately tight.

At that point, the "mechanic" may: 1. Tighten it more, subjecting the bearings to excessive preload, and therefore early bearing failure,

2. Leave the nut insufficiently tight, and hope it does not loosen in service. Expecting this scenerio, experience should have caused him to slather the threads with Loc-Tite,

3. (CORRECT PROCEDURE): Remove the nut, washer (if present), U-joint flange or yoke, oil slinger washer, front pinion bearing. The crush washer then will be visible, and MIGHT be removable by sliding it off the pinion snout. New crush washer installed, reverse assembly process. Insurance? Replace nut with new, "prevailing torque type" (self-locking), use Loc-Tite if desired. Tighten nut until preload is within specs. That will take well over 100 ft.lbs. applied to the nut. It WILL NOT loosen in sevice then.

Lots of words here, sure. But it covers most of the novice-type questions and uncertainties. Surely, there are many mechanics replacing leaky pinion seals who do not yet understand the dual-function of that nut. I truly feel sorry for you several who have had bearings fail after a "simple" seal replacement job. imp

I watched my mechanic do the job (off the clock, so it was cheaper) and I certainly do not recall him removing the pinion bearing. Just the nut and the seal.

Is the front pinion bearing as easy to get to as it sounds, i e, no disassembly of the pumpkin (other than disconnecting the drive shaft, of course)? Doesn't the bearing need to be pressed on? Would I have to drop the diff anyway?

It took him about 45 minutes (talking in between, double checking seal fit, etc) to do BOTH the front and rear pinion seals.

Would replacing just the front pinion bearing be a reasonable bandaide while I decide my ultimate course of action?

 

[matt0248]

Here is the problem, You cannot get the bearing race out without removing the pinion gear itself. so just by replacing the outer roller bearing and using the old race will cause premature bearing failure also. In order to get the CORRECT bearing preload the carrier needs to be out, thus allowing the pinion to rotate by itself. Most maintenance manuals have bearing preload spec's for new AND reused bearings. You MUST tighten the pinion nut until the crush sleeve just starts to compress, then check the prelaod with an inch-pound torque wrench to see where you are at. To increase the preload tighten the nut more. Sometimes it does require a lot of force on nut to get the correct prelaad. But just tightening the nut to a specific torque will not, in most cases, result in the proper pinion bearing prelaod.

 

[imp]

Is the front pinion bearing as easy to get to as it sounds, i e, no disassembly of the pumpkin (other than disconnecting the drive shaft, of course)? Doesn't the bearing need to be pressed on? Would I have to drop the diff anyway? Usually, but not always, the front pinion bearing is a "slip fit" on the pinion, and thus can be slid out and off, if gripped in some way. Sometimes tapping it with a drift, will cause it to bounce forward a bit, enought to grasp it. Sometimes tapping the end of the pinion with a rubber mallet will, due to clearance between the gear teeth, cause the bearing to "pop forward" a little bit. What is said below about the outer race, which is pressed into the center section casting, is absolutely true. However, if the front bearing proves removable, the outer race may then be inspected to determine its suitability for re-use. Remember, we started the discussion about replacing only the seal, not a bunch of bearings! Make any sense?

Would replacing just the front pinion bearing be a reasonable bandaide while I decide my ultimate course of action? Muy no comprende! If bearing is bad, replace. If outer race is bad, tear apart or replace center section.

imp

 

[Dalmus]

Makes perfect sense. And is certainly not something that I would do myself!

So it comes back to the fact that at 150K with a bad bearing, it makes more sense to replace the entire diff than just the bearings.

I'm finding it rather interesting that its a hard to find rebuilt diffs for the XLS. Plenty for the sport tracs...

 

[1989dangeroustoy]

I rebuilt my rear end for $90, just the cost of bearings .if you have access to a press and can do basic mechanic work you can rebuild a rear end. I recommend pulling the whole axle unless you have a car lift. Hardest part was removing the old bearing races with a punch and mini sledge, you can even buy a press from harbor freight for around $100
What do you have to lose, if by some freak accident you Jack up your out $90 and atleast your learning something!

My two cents!

 

[matt0248]

Makes perfect sense. And is certainly not something that I would do myself!

So it comes back to the fact that at 150K with a bad bearing, it makes more sense to replace the entire diff than just the bearings.

I'm finding it rather interesting that its a hard to find rebuilt diffs for the XLS. Plenty for the sport tracs...

Check Zumbrota Bearing and Gear. I think the website is www.zbag.com

part number 440-1384D you have to call for price though.

 

[Dalmus]

Check Zumbrota Bearing and Gear. I think the website is www.zbag.com

part number 440-1384D you have to call for price though.

Thanks for the reference. I don't think 1384D is correct, as its for a locking diff, and I have the LS. I think I would need 440-1384C?

Obviously the sooner I get this taken care of, the better. I'm hoping I can get at least a month out of it as-is so I can pull the cash and time together!

I am liking 1989dangeroustoy's idea, though... I've seen bearing kits on NAPA and Advanced Auto for roughly those prices (depending on how in-depth I want to get). I'm fairly certain I could dismantle everything after taking a look at the Chilton, but I've never worked with a press before, so I'd like somebody to shadow me on that one. Is this basically an all day Saturday kind've project (if all goes well)?

Even if I spend $200 and get another year out of it, its well worth the money, right?

 

[imp]

Replacing the Bearings

Dalmus, I don't want you to feel I'm beating a dead horse, but:

There are 2 things likely to "bite-back" if pinion bearings and differential carrier bearings are simply mechanically replaced.

Both are related to manufacturing tolerances varying enough from bearing-to-bearing, that operating specs for the gears may wind up out of whack. The rear pinion bearing (closest to it's teeth), determines, along with the differential side bearings, both gear-tooth contact pattern and tooth clearance (back-lash).

Explained more graphically, given two identically-numbered bearings, cone & roller assembly and outer race, the actual assembled "thickness" of the bearings may vary by several thousandths of an inch: this is enough to mess-up gear operation.

Thus, installing new bearings, to get a most-reliable result, requires careful adjustment of the interaction of pinion bearing preload, pinion location within the case, ring-gear (differential carrier) bearing preload, and ring gear location, to obtain acceptable gear-tooth mesh pattern and backlash. Improper contact pattern or backlash, will result in gear noise. imp

 

[Dalmus]

Feel free to beat the horse! I asked the question here so that I can get the opinions and experience of people far more knowledgeable than I.

I'd like to expand on the tolerance issue a bit. Assuming the two mating gears are are within manufacturing tolerances, but still off from each other, is there a risk of catastrophic failure, or would it simply be noisy?

Worst case scenario, these are the options I see:

1- Do nothing, and risk catastrophic failure at anytime, tomorrow or 20,000 miles from now.
2 - Attempt the shadetree fix to save money but risk either a noisey diff for the remainder of the truck's life OR failure at some random point in the future.
3 - Install a professionally rebuilt diff myself for 4x the cost but (in theory) have no diff worries for the remainder of the truck's life.

Oy... Decisions. I wish I could be sure her engine would last another 50k! Would make this easier!

 

[ShawnTRD]

We just had our rear diff replaced with a reman Jasper for $2200 with tax. It was $1600+ for the rear diff and amost $400 for labor. They did say they discounted the rear end about $200 for me. Another shop told use $2500 for a Jasper about a year ago.

 

[boominXplorer]

It cost me about $350 to rebuild my rear diff in my 04. I replaced the bearings, clutch packs for the l/s and replaced all seals with updated ford ones.

If you remove the diff yourself you should be able to take it to a driveline shop and have it fully rebuilt for under a grand

 

[imp]

I'd like to expand on the tolerance issue a bit. Assuming the two mating gears are are within manufacturing tolerances, but still off from each other, is there a risk of catastrophic failure, or would it simply be noisy?..

These gears are technically known as "hypoid gears", which means the pinion operates below the centerline of the ring gear, if you can picture what that implies. This creates the unusual condition where a bit more than just one pinion tooth is engaged with ring gear teeth at the same time; in other words, the tooth contact area is greater than for plain bevel gears (right angled gears). This adds strength, and the more important fact that the spirally-curved teeth of the pinion may be made such that instead of rubbing against the ring gear's teeth, they actually roll over them, like weird-shaped rollers. This creates great strength and unusually quiet operation as an advantage, but with the disadvantage they must be held closely in alignment to each other, the slightest deviation from correct tooth contact resulting in a singing-like whine.

Now, having run-on at the mouth maybe too much, regarding your question: Every pair of ring and pinion gearsets is unique, in that they are ground and lapped on special Gleason Gear Machines and kept strictly together as matched pairs. Variations in dimensional size from pair to pair can be pretty great-- so much so, that the shims used to locate the pinion in the housing may call for a difference of perhaps 0.020" (almost 1/32") from one set of gears to another. Thus, if a set of gears is replaced, the old set of shims used with the replacement gear set might produce terrible noise, and/or early gear failure. Changing only bearings often re-locates the teeth unacceptably enough to cause major noise.

So, to answer the noise/life question: In general, noisy gears, where the noise is caused strictly by misalignment not resulting from worn bearings allowing "wobble" between the gears, will continue to "sing" unchanged for many thousands of miles. Keep in mind though, we're talking generalities here: ideally, the tooth contact pattern under no load is approximately centered on the tooth faces. As misalignment moves the pattern away from center, it can greatly weaken the strength capability of the gears while producing whine. In short, gear whine is aggravating, but if caused specifically by misalignment not resulting from bad bearings, it does not indicate pending gear failure. imp

 

[Dalmus]

Thanks, Imp.

That was a very good explanation of the ramifications of doing a fix "on the cheap."

I'm going to have the pinion nut checked first, before I do anything else. I know its a shot in the dark, but its a cheap shot worth taking... I know he cranked it, but I don't recall him using locktite. I also might have him see if he can pull the outer bearing and inspect it as you suggested earlier. Although as I look at pictures of the differential, it may prove to be quite obnoxious to do without dropping the diff.

If I can source a decently-priced rebuilt differential assembly, I think I'd prefer to just swap diffs rather than worry about replacing the bearings, and then a couple months later the packs go, etc.

In the meantime, I'll just limit my driving as much as possible. Oh, the joys of car ownership!