1999 Suburban diff is singing, not sure my options. Reman diffs?

[redfishsc]

Truck--- 1999 Suburban C1500 (2WD), 5.7, 206K miles, worth saving. Engine in excellent shape, clean truck. I take the family on week long camping trips 300 miles from home, so I really want to keep the truck in reliable shape.

Rear end is G80 locker, 3.43 ratio (that I don't like), 10 bolt. 5-lug wheels, drums. Truck actually drives very nicely. You don't feel anything in the drivetrain that says "somethings wrong".


Rear differential has been singing on deceleration, particularly if I'm coasting in lower gear. Sound is NOT chunky/crackling. Instead, it simply sounds like someone has laid a stick of rebar on a spinning driveshaft. Not a sharp squeal, but a dull metal scrubbing sound. There's also "some" noise while moving forward but I cannot tell if it's the diff, or if it's just normal road noise, or just normal drivetrain hum on an old truck.

You mostly hear it with windows down, it's not overly loud. You can only barely hear it with windows up. Been sounding like this for several months, but it was only this past week that I realized it was the differential.

I also hear a "clunk" that happens when I'm pulling up to (or, pulling away from) a stoplight. Maybe it's the slip on the yoke reseating, maybe not, but perhaps it's the pinion that's been loosened?

I have not yet inspected the U-joints, and the drums do not have anything in them scraping.

Two weeks ago I removed the diff's cover. Oil in it was fine, still even slightly clear. Not sure how many miles but it was at least a couple years old. The ring gear looked fine to me. The magnet only had "metal sludge" on the magnet. I don't know what's normal, there were a couple tablespoons of silvery metal sludge on the magnet. NO chunks or shavings. Refilled with Mobil1 gear oil.


My suspicion is that the pinion nut has come loose (for whatever reason, maybe weak crush sleeve?) or the pinion or carrier bearings are going out on me.

Either way, locally I've been quoted $1200 just for a bearing swap (no new gears). Local salvage yards are few here in Charleston, not easy to find a used rear end to swap.

Are there reputable online places? I've considered buying one from Weller, Powertrain, etc but swapping the rear is a HUGE amount of work for me to do myself just to get a reman diff with a poorly calibrated backlash.

I've never had to work on a rear end before, so any advice is appreciated.

If I swap it, I'm likely to go with a 3.73 since I occasionally tow a camper, and my daily commute is only 5 miles. I'm not too fond of the 3.43.

 

[RichLo]

take the diff cover off and stuff as many banana peels in there as you can fit, put the diff cover back on and fill the rest with Lucas Oil Stabilizer.

 

[90halfton]

Pulling up to and leaving a stop sign clunking is carrier bearing ( could be your other issues too. Get under it and wiggle your driveshaft I'd be willing to bet it mover around in carrier waaaayyyy more than it should.

 

[magimerlin]

Just fixed having the same symptoms... growling noise and clunk at stop lights.... put the ebrake on (or block the wheels), put it in neutral and check your ujoints.... my back one had a little play but my front one was another story.... it was as loose and worn in as a ***** in an old western saloon.... I replaced all(in my case 2) u-joints on the rear shaft... all noises and chunks gone.....

sent from what use to be a great country...

 

[redfishsc]

Thanks for the help guys, I will get under it this Friday and see if the ujoints are shot. Would be nice if that's all it is.

That being said, I have enough suspicion that it's the diff that's going out.

I'd also like to use the opportunity to swap the 3.43 for a 3.73 or maybe even a 4.10.

If I find a used one from a truck somewhere locally, will I be able to reinstall the Suburban's sway bar? The trucks didn't come with the sway bar, I believe.

 

[redfishsc]

take the diff cover off and stuff as many banana peels in there as you can fit, put the diff cover back on and fill the rest with Lucas Oil Stabilizer.

I tried this but it didn't work, but the bananas were pretty green. My cousin ***** told me not to use Lucas, he always filled his pumpkins with Seafoam and Motor Honey.

 

[redfishsc]

Pulling up to and leaving a stop sign clunking is carrier bearing ( could be your other issues too. Get under it and wiggle your driveshaft I'd be willing to bet it mover around in carrier waaaayyyy more than it should.

At first I didn't follow what you meant, but I think (because I'm a noob at rear end names) the part you are calling the carrier bearing is not the bearings inside the differential housing. I've seen those referred to as carrier bearings on several tutorials.

You're referring to the center support bearing, meaning, the one where the differential and driveshaft mate up. Correct? I do appreciate your help.

 

[90halfton]

At first I didn't follow what you meant, but I think (because I'm a noob at rear end names) the part you are calling the carrier bearing is not the bearings inside the differential housing. I've seen those referred to as carrier bearings on several tutorials.

You're referring to the center support bearing, meaning, the one where the differential and driveshaft mate up. Correct? I do appreciate your help.

It's the rubber mounted bearing/support halfway between your transmission and differential. 2wd models use these to support the center of the long double jointed driveshaft. There are two 3/8" (?) Bolts that hold it to a cross member that spans from left side of frame to right. I would imagine you can grab the driveshaft by that thingy and Waller it around inside that carrier, and that may be the thumping around at low speed accelerating and decelerating. Not promising this is your problem, but this does happen alot on these trucks and I would definitely troubleshoot before throwing a thousand dollar axle job at a problem that may not have been related to the diffy.

 

[redfishsc]

Actually my Suburban has the single piece aluminum shaft, so that's not the issue.

I'm back to square one at the moment. Local shops want $1500-2000 just to swap the internal bearings on this, and that's hoping the ring, pinion, and G-bomb diff aren't worn enough to need replacing.

I jacked it up today and got under it, thinking about swapping it with a salvage 3.73 complete rear axle that's available, but that's going to be just a bit outside what I feel comfortable tacking alone for the first time.

I may end up biting the bullet and still paying the shops to do this. I could do it if I had the time and an experienced helper. Painful decision, this is a lot of cash to spend on an old truck like this. Everything else on it is in very good shape.

 

[magimerlin]

Did you check the u-joints like I recommended... you seem so stuck on it "BEING" the rear end and nothing else, it seems like you dont want it to be anything but that.. and are stuck I think because you want 3.73 gears as you mention them a few times already... if you checked them as I described what was the outcome?? Remember you must put it in neutral with the ebrake on "OR" lift the rear so both wheels are off the ground without ebrake on... first way is alot easier though... then get under there and shake and try to spin the shaft.. grab right by the ujoints so you can see and feel any movement..

sent from what use to be a great country...