rear differential carrier bearings

[Superdawg]

175k on a 2004.5. Daily driver for first 13 years. Tows 10k fifth wheel occasionally. Changed rear diff fluid every 50k or so.
Been hearing a low roaring sound that started 1 1/2 years ago. I threw some parts at it, because that is what I do sometimes..... Front wheel bearings and outer rear axle bearings. Seemed to quiet it down a bit. Went from CA to Washington (towing) and back and heard it a little. So Cal to the Sierras and back towing and heard it again. It finally was pretty audible driving about 20 mph unloaded. Put it up on my buddy's shop rack and the roaring sound seems to be focused on the bearings on both sides of the rear diff.
Going to have him replace the inner and outer rear axle bearings and races soon. Hopefully the differential is fine when they get in there. I do most of my own work but I read through the instructions on this job. Not for me this time.

 

[Timd32]

For a while we had a bunch of trucks with bad Pinion bearings, they would make a pretty deep low howling noise, at hwy speed when really bad it would drive you crazy.

Someone will chime in most likely on these trucks.

The internet is pretty bad at sound and feel of the pants issues, but you could feel these when cruising. The noise was low.

 

[Superdawg]

I just looked at a diagram of an AA rear axle. I think the correct term is the differential side bearings. Sorry about the title.

Diagnostics at his shop: We lifted the rear axle in the air and put it in gear. Using a stethoscope and by feel with our hands, it is most pronounced at both sides of the differential. If its coming apart, it would make sense to replace the pinion bearing too?
The sound/vibration seems to go away at the outer end of the axle, the pinion and up the rear driveshaft.

 

[Timd32]

At first we went just parts swappers and went overkill and did everything, the next one we got a whole used rear, the 3rd one we were like maybe we need to figure this out.

These were all different trucks same rear, some pulled hard, some never.

I'm not sure how we figured out it was just the pinion bearing, it might have been pretty obvious when we had it apart and everything was newer.

Someone will chime in I'm sure to see how to maybe isolate the issue.

 

[sag2]

You will know when you take it apart. If it has been going bad for a long time there is a good chance all the bearings have damage from metal going through them. When you drain the oil see how much metal is in there, and then determine if the metal is from the carrier bearings. If it is you are probably better off replacing the pinion bearings while your there.

 

[Superdawg]

Thank you all for the advice. I have been good friends with the shop owner for 42 years so I will get the straight story when the diff comes apart.

 

[MGroft]

I have taken out my carrier bearing. 1 solid tube with two universal joints at the end no problem. Is been done here in Vegas by Dan's Driveline

 

[Superdawg]

Here is the update. Both rear differential carrier bearings had wear and were replaced. Also replaced pinion bearing while in there.
I had just replaced both outer axle bearings last year so those were cleaned and reused. Just very small bits of metal in the bottom of the differential. Used Oriellys Master Pro GL-5 75w90, no LSD additive

No more roaring sound. Nice and quiet, well, as quiet as can be. I didn’t take a picture of it but where the ring and pinion meshed up it looked good.

 

[Superdawg]

Well, I noticed this thread made it into the latest TDR magazine and I am late on an update. I wish things were still rosy. We took a 3,000 mile towing (10k trailer) trip to Colorado in August. I started to hear a grinding sound coming out of the rear end during the trip while turning sharp right or left, not on straight takeoffs. As the trip progressed, the grinding sound/feel in the drivetrain lasted longer, up to about 3 seconds. Rear diff oil level was fine and no higher temps than 175 if I remember correctly.
Unloaded it makes no grinding noises turning right and left.
I removed the rear diff cover and it was very dark (clutch material from the LS unit?). Only 3,000 miles on the oil. Also there were quite a few metal shavings in there. It was 75w90 w/ no additive. I talked it over with a shop that does rear ends and they suspect the limited slip unit. Their suggestion: toss the AAM limited slip unit out and put in a locker with new bearings and races all around for about $1800-2000. I have not actually driven the truck into a diff shop to have them diagnose yet.
When not towing, the truck gets very little use. So here it sits until I take it in.

 

[cerberusiam]

The AAM axles do not have a clutch type limited slip to burn up. They are TQ-bias type with gears and 6 little brake pads not clutches. If you have metal in the fluid the bearings or gears are burned up and chewing themselves apart. Might be easier to look for a later model low mileage diff from a salvage yard. At a little over 300k mine was totally hammered due to just what you describe at 80k. We did not get it right the first time, learned a few things and went thru 2 sets of bearings to get it right but sure that contributed to the total disintegrating in the diff. Picked up a 160k diff for less than I could by the rebuild parts.

 

[Superdawg]

Hmmmm. Thanks for the suggestion. This is a 3.73 rear end in a 2004.5 2500. What years of trucks would I be looking for to be compatible with mine?

 

[CVR222NV]

If you are changing the rear diff you might think about upgrading to a Eaton Detroit Trutrac especially if you will be doing any off-roading at all (or snow or mud conditions). I have put mine through a lot with no issues at all. It is a more expensive option but well worth it if you can afford it.

 

[cerberusiam]

A 2500 or 3500 thru 2004-2012 will work IIRC. All the 3rd gen years will work, not positive on the early 4th gens but I believe they are compatible until the air rides became available. Have to check the salvage cross ref to make sure and make sure it has the gear ratio you want.

 

[Superdawg]

Thanks for the info. Now to weigh the costs/advantages of a rebuilding mine or buying a used part.

 

[AH64ID]

It's possible that there was still metal in the housing, even if it was cleaned out. I had this happen to me on a '95 4Runner where the rear diff wasn't assembled correctly, the 2nd one had the bearings fail due to insufficient cleaning of the housing..and I cleaned the bejesus out of it!!! It had been removed, washed, etc.

Also, 50K miles is a bit more that that fluid is likely good for. With frequent towing, as you have mentioned, it's a 15K miles change interval. I'm not saying the extended interval caused the initial failures, but it's worth thinking about. These axles are very strong, and Dodge spec'd them with better bearings than GM did.

If you want to run extended drain intervals I'd look into a better quality gear lube, like the Amsoil or Redline products.

 

[Superdawg]

AH64ID, Thanks for that info.
I am hesitant to go through the labor and expense to put in a used part. I may not have the truck forever but the next guy will appreciate a quailty job on the differential.
I stopped by a differential shop yesterday and he stressed the same thing about cleaning. He was not a fan about my previous replacement of just the bearings. His recommendation was to put in the Eaton Truetrac (only one he recommends), full bearing/seal kit and a full cleaning of the diff/axle with 8 hrs labor. 2,300.00
I still need my truck for towing the trailer but the use on it is down to about 3-4k miles per year. I'm going to get another quote but I am liking what I read/heard about the TrueTrac.
This time, I will take it to a differential shop, not a general automotive shop. I am in Orange County, Kalifornia.

 

[AH64ID]

I’m happy with my OEM LSD, but if it ever goes out a Tru-Trac is going in it’s place.

 

[cerberusiam]

That is the problem with rebuilding, parts are expensive and labor extensive. A good low mileage rear axle can usually be had for $500-700 if you shop around.

 

[Blakers]

The rear end in my 03 with 315,000 miles has gotten noisy, however it does not seem to be bearing noise, but rather gear lash noise. It makes noise under load and during a downhill coast, but not at a steady load. I replaced the wheel bearings last spring and had the case open. Everything looked good inside, except the pinion bearing has a little too much play.
I used to put a lot of miles on the truck, but this last year it's only gone about 10,000 miles. I'm not sure how much I should be worrying about the noise. Perhaps I just keep my eyes open for a good lower mileage junk yard axle? I bought the truck new and it runs great and it's in good shape, but the transfer case is going to need serviced, and who knows when it's going to need injectors. I still think it's worth spending money on compared to a newer one.

 

[Superdawg]

Update for those watching this saga. I have decided to replace the LS with an Eaton Trutrac. I have a preferred diff shop lined up but COVID has sidelined some of their workers so I have been waiting patiently for a good time to bring it in.