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  1. #1

    Default 99 Suburban Rear Differential help

    I have a 99 Suburban, 4WD with rear differential noise.

    I know it has a 3.73 ratio (from research done a long time ago) with a 10 bolt rear differential.

    1st off.. HOW THE HECK DO YOU CHECK FLUID LEVELS? I've probed around with my fingers and can't find a filler hole or fluid check hole.

    I've got noise coming from the rear differential. The paint/coating looks like it's been baked pretty hard, and is peeling off.

    I've never done a differential before, and am at a loss to know where to start in looking at this.

    The noise is pretty bad. It almost sounds like when I had a brake collapse with parts scraping inside the drum. I have the sub up on rear jacks with front wheels chocked.. Ran it in drive, and the noise is loudest in the rear differntial case, but sounds loud out on the axles as well.

    Are there common failure points? How to check the fluid level? Is it better to just try to find another rear differential than to mess with this?

    I have no idea if my daughter may have caused any damage.. She took the truck off roading and ran it through soem pretty rough areas, causing a big wood stump to push the driver's side floor up about 5 inches, front bumper knocked in and up.. etc. I have no idea if she had gotten stuck somewhere and gunned it trying to get out.. or anything. She to this day denies everything, but was the sole driver at that time, and the floor just 'mysteriously' grew that hump.

  2. #2


    Quote Originally Posted by jmasters View Post
    I have a 99 Suburban, 4WD with rear differential noise.

    She to this day denies everything, but was the sole driver at that time,
    Reminds me of when I was a teenager and ripped the front end off of my stepmom's Prelude. Told them I went into a McDonalds and when I came out, it was like that!

    Sorry I don't have the answer for you. Just funny to see that teenagers (I am assuming she is) are the same everywhere!

  3. #3
    Legend unplugged's Avatar
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    Sep 2006
    High Deserts of SoCal


    I suppose you could craft some sort of dip stick, but just pull the fill plug and the oil should be filled to the level of the plug. The plug will be on the side of the differential housing as in this pic:

    At this point it would be worth removing the cover to inspect for damage and change the oil.
    Remove the 10 bolts and gently probe around the cover to loosen it. (Don't force it)
    Signs of metal shavings are normal. Chunks of metal aren't. Not worth rebuilding for the amateur. A competent diy could rebuild the rear end, but it is easier for most to go the junk yard route.
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  4. #4

    Default Followup

    Thank you for the great pics! I did find the filler/level hole, and since the suburban was pointed downhill just slightly, fluid came out. But the fluid smelled SERIOUSLY burnt and was black too.

    I'm a pretty competent DIY'er.. having rebuilt trannies and done a few head gasket repairs (one on the road during a vacation).

    I've just never messed with a rear differential before, or axles like this.

    The factory service manual I have goes out of its way to NOT show me the filler hole, and also says that differential/axle noise is VERY difficult to troubleshoot even among well experienced techs... so I'm wondering what makes it so darn hard to track down..

    I looked on for rear axles.. and they're not cheap!!!

    I suppose I can try looking at a local pick-n-pull. See if they have anything that matches.. looks like from that a large number of years match. but I'm not sure what other aspects besides 6 bolt lugs and 3.73 ratio that I'd have to look for.

    where I don't like messing with axles, is when I have to start pressing in bearings, etc. and I dont' have the proper tools. I have a bench press but it's hokey, to be honest with you.

    it doesn't have much throw...

  5. #5


    Well, the junkyard route is the easiest.....but....I say try to do it yourself. The reason is simple, you don't have anything to lose. It's already dead. Pull that 10 bolt back cover off and check back with us. We can walk you through it. You can always back out before you spend any money, right?

  6. #6


    You definitely want to open that up before you start making plans for a new unit. It's likely the problem will be painfully obvious.
    When you hear hoofbeats, look for horses not zebras.

  7. #7


    Quote Originally Posted by TheTransportGuy2 View Post
    Well, the junkyard route is the easiest.....but....I say try to do it yourself. The reason is simple, you don't have anything to lose. It's already dead. Pull that 10 bolt back cover off and check back with us. We can walk you through it. You can always back out before you spend any money, right?
    On the flip side, you do have something to lose.... a lot of money. Differential gear sets are very difficult to set up properly, even for seasoned professionals. It's not easy at all to make sure the ring and pinion are getting the correct gear pattern with each other. Incorrectly setting the gears can at best cause an annoying whining-type noise and at worse lock up and shatter the gears. If you're sure it's the differential causing the noise and not u-joints or possibly the transfer case, I'd go the junkyard route for a used axle out another truck with the same gear ratio.

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 277K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

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  8. #8

    Default New info

    I pulled the back cover. Didn't see any obvious broken parts.. but DID notice the pinion gear "wobbles" a little. I saw that there was "writing" on the edges of the ring gear and pinion gear.. leading me to think someone (before me) tried to do a replacement and botched it.. unless the writing is from the the factory so that people wouldn't install the wrong parts..

    Tried looking around on this site for more info, and one poster said that the carrier (huh?) would need to be replaced. Looking up prices, I could see this getting expensive..

    Went to a pick and pull, and after searching for an hour, I FINALLY found an unlisted vehicle in their database which had the right differential. (as a different question, I found a Chevy pickup (Cheyenne) that had a GT4 in the glovebox code.. but didn't know if it was compatible.. it wasn't listed as such on my little printout at pick-n-pull)

    I am concerned that it too as a coating that looks baked off.. suggesting high heat. I rotated the hubs and didn't hear any growling.. but.. don't know if I can expect to hear anything with hand movement.

    I couldn't quite get it all uninstalled.. the e-brake cables were attached.. and I didn't want to have to undo everything in the drums, and didn't have a cutting tool to go through the cable... I'll be back tomorrow early AM to get it. (the employee there kept telling me he was totally shocked that differential wasn't already gone that day... sounds like they're common failure items??)

    I'm a little concerned as well. There's evidence of past leaking.. but it may come from the rubber plug area that someone put into the back cover. I'll prolly just put my original cover on in its place..

    I'm pulling this myself.. and am a little unsure how I'm gonna handle this.. I don't know how heavy it is.
    I'll try to get my son in to help me tomorrow AM early.

    Thank you for your offers of help.. I think I may (for the purpose of learning) try to look at my original axle to see what is going on. I'll possibly keep it around in case this junkyard axle doesn't work... Course, I don't relish having an axle around either. LOL We have CC&R's here.. and I just don't want to make my yard look further like a junkyard.

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