Diagnosing Rear End Noise 2003 Suburban

[arc_wiz]

I've got a 2003 5.3L 4x4 Suburban. I replaced the differential fluid in the front and rear with AC Delco bookspec fluid (https://www.amazon.com/gp/product/B000QGOX1A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) no LSD additive. Since then (I think) I notice a slight whining or groan when I turn right from a stop and it goes away once I straighten out. This only happens after I drive highway speeds for a while or drive around town for a while (30 mins or so) and it doesn't always happen. When I start driving around no issues. When driving at highway speeds everything sounds normal. Driving normal speeds windows down no issues or unusual sounds.

I was looking into this thread but not the same problem to me afaict. https://bobistheoilguy.com/forums/threads/rear-end-noise-2003-suburban.349849/

I've done the transfer case pump rub fix already with the billet replacement ring and jbwelded the little hole that created years ago, no issues since then afaict. (https://www.amazon.com/gp/product/B00F7SIG3S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)

Any suggestions? Not sure if its a diff issue or a wheel bearing or something else. When I replaced the fluid in the diff it was overdue, but no chunks or shiny fluid. Just old fluid afaict. Differential looked normal, I would have taken a closer look had I known this was going to be an issue. It has been a while since I did the job maybe a year now? Car runs and drives just fine other than this issue.

I filled it to 5/8 below fill hole as per the manual, but it was filled to top of fill hole before that.

Thanks for any help!

 

[D60]

Hmm, I don't know. A noise after turning right and intermittent....could be a lot of things.

I guess if you're sure it coincided with the fluid change you could try to mix it up a little just to see if anything changes. You could throw in some LSD additive. It's good stuff and won't hurt anything in an open diff or GovLok. And/or you could try maxing to the bottom of the fill hole.....again, just to throw in a variable and then see if a change is observed.

I always thought the below-the-hole thing was dumb and lots of guys ignore it even if they know about it.

If you don't want to do any of that I guess I'd start by jacking up all 4, check for any noise or excessive resistance while rotating and shake each looking for wb play.

Do you have the stupid Auto t-case? They love to do dumb things when turning tight, even on dry pavement. You'd have to be in "Auto" though

 

[arc_wiz]

I have an auto t-case, but I leave it in 2wd or manually select 4wd hi/lo,

I'll could try filling to the top I suppose that is easiet and I have left over fluid. I have heard that can cause the pinion seal to leak, but like I said mine was like that for almost 200k miles..

The debate on the LSD adds is fierce online, I'm open to trying it. Its a G80 (heavy duty locking differential) per the parts sheet. I think that would be the gov-lock, but its been a while since I had it open and I don't remember.

-M

 

[arc_wiz]

> Hmm, I don't know. A noise after turning right and intermittent....could be a lot of things.

Ya.... tough one

 

[PontiacHO]

Front wheel bearing and/or hub bearing going bad can be heard when turning…sometimes. I’ve had blower motor with bad bearings
Bushings get noisy in turns. Changing diff grease wouldn’t cause unless you didn’t get it full and now have a carrier or axle bearing going bad. Have you checked the level again? Your diff does not need the limited slip additive.
Never have 4 wheel drive engaged on dry pavement.

 

[Oliveoil2]

What does your owners manual say?

 

[arc_wiz]

Say about what, would you mind clarifying a bit more?

 

[arc_wiz]

> Have you checked the level again?

Yep not leaking still at 5/8 below the hold.

> Your diff does not need the limited slip additive.

That was my understanding. I have the service data and it just says fill with the specified fluid or eq (GM 12378261) (use the same stuff front and back) (AC Delco 10-4016 is the replacement).

> Never have 4 wheel drive engaged on dry pavement.

I generally don't. I turn it on once a month or two for about 10 seconds and idle forward just to lube up the front.

 

[oldhp]

Correct me if I'm wrong. But a G80 locking differential "does" have clutches in it. Not clutch packs as in a full limited slip. I would drain it, put in 2ozs limited slip additive and fill with your favorite Full Synthetic 75W90 gear oil that has friction modifier in it. I like in order Redline, Valvoline or Mobil1. I'm sure Amsoil is good just have never used. Fill to the bottom of the fill hole or 5/8" below ain't gunna make a difference. A GM mechanic told me this 5/8" low was done for MPG. Their shop always filled until the oil dribbled out. Good Luck!!!!!!

 

[LDM]

Correct me if I'm wrong. But a G80 locking differential "does" have clutches in it. Not clutch packs as in a full limited slip. I would drain it, put in 2ozs limited slip additive and fill with your favorite Full Synthetic 75W90 gear oil that has friction modifier in it. I like in order Redline, Valvoline or Mobil1. I'm sure Amsoil is good just have never used. Fill to the bottom of the fill hole or 5/8" below ain't gunna make a difference. A GM mechanic told me this 5/8" low was done for MPG. Their shop always filled until the oil dribbled out. Good Luck!!!!!!

G80 should not use any limited slip additive as it is not a posi-style rear end. GM specifically states not to add any limited slip additive on the G80 locking diff. 75W90 is the correct fluid for an 03 GM G80 rear end.

As far as the noise, sounds more like a wheel bearing than a rear diff. I'd try to pin point where the noise is coming from and go from there. If it is a wheel bearing changing the diff fluid wouldn't have any effect.

 

[oldhp]

G80 should not use any limited slip additive as it is not a posi-style rear end. GM specifically states not to add any limited slip additive on the G80 locking diff. 75W90 is the correct fluid for an 03 GM G80 rear end.

As far as the noise, sounds more like a wheel bearing than a rear diff. I'd try to pin point where the noise is coming from and go from there. If it is a wheel bearing changing the diff fluid wouldn't have any effect.

But he changed rear fluid and then noise started. Coincidence wheel bearing goes out then??? Maybe. GM says "don't add any friction modifier" but no mention of using gear oil with FM in it. I had a 2020 Colorado and put Redline 75W90 full syn with FM in it. Quiet as a church mouse and when I went thur ditch at 45° the one tire came off the ground, spun a tad and rear end "locked" in with no noises at all. There are lots people using FM gear oil with no problems. Noise started with fluid change. Go back to full synthetic gear oil with FM and see. That's what I would do.

 

[LDM]

But he changed rear fluid and then noise started. Coincidence wheel bearing goes out then??? Maybe. GM says "don't add any friction modifier" but no mention of using gear oil with FM in it. I had a 2020 Colorado and put Redline 75W90 full syn with FM in it. Quiet as a church mouse and when I went thur ditch at 45° the one tire came off the ground, spun a tad and rear end "locked" in with no noises at all. There are lots people using FM gear oil with no problems. Noise started with fluid change. Go back to full synthetic gear oil with FM and see. That's what I would do.

GM specifically states not to add any friction modifier to the G80 locking differential as most gear oil already has some in it. Adding additional friction modifier to the G80 locking diff can cause it to not function properly and improperly lock/unlock. Just because you added it to your G80 and it seems to work properly does not mean it is a good idea.

 

[Lyman]

I have had a problem with rear-end noise only when turning. It was very hard to diagnose. It ended up being carrier bearings.

 

[D60]

I have had a problem with rear-end noise only when turning. It was very hard to diagnose. It ended up being carrier bearings.

Because you said rear end I'm going to assume differential carrier, not driveshaft carrier bearing. Just good to clarify

 

[arc_wiz]

10-4016 75w90 is full syn ?

 

[arc_wiz]

Thanks for the help so far everyone, seems like a tricky one. I'm not opposed to trying a different fluid. I just followed service data. I did call a dealership to ask them which fluid they put in. The guys local here said they used mobil1. I ended up buying the ac delco anyways but I specicially called them to ask about FM, they said they didn't know. hah

 

[Lyman]

Because you said rear end I'm going to assume differential carrier, not driveshaft carrier bearing. Just good to clarify

Yes, differential carrier bearings

 

[oldhp]

GM specifically states not to add any friction modifier to the G80 locking differential as most gear oil already has some in it. Adding additional friction modifier to the G80 locking diff can cause it to not function properly and improperly lock/unlock. Just because you added it to your G80 and it seems to work properly does not mean it is a good idea.

Ummmm........................I didn't add FM. The Redline 75W90 has FM already in it, as do most full synthetic gear oils. Done.

 

[LDM]

Ummmm........................I didn't add FM. The Redline 75W90 has FM already in it, as do most full synthetic gear oils. Done.

You specifically suggested to add 2 oz of limited slip additive in your 1st post, which is exactly what GM says not to do. I said this is a bad idea, which is it, as it goes against exactly what GM recommends for the G80 locking diff. Regardless of what you do with your vehicle, adding limited slip additive is a bad idea on the G80 locking diff.

 

[arc_wiz]

Dang, carrier bearings are essentially a rebuild.. You'd have to reshim swapping bearings correct?