99 GMC Suburban - 1500 - Rear Differential blow out

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by JoeM, Feb 1, 2011.

  1. JoeM

    JoeM New Member

    I'm looking for some advice regarding an on-going issue I've had with the rear differential on this vehicle. I recently had the rear differential replaced by my mechanic. Supposedly the case on that one had a "pin-hole" in it, went dry and eventually failed. The mechanic thankfully replaced it his cost - but not before trying to insinuate that it must have been something I did.

    It'd been driving fine until - A few days back, after having the truck idling in PARK for about 15 minutes or so, I shifted gears into DRIVE, moved forward about 5 feet when the wheels locked up - almost as if it was slipping back into PARK on its own. It would drive in REVERSE just fine. After jagging around for a while with putting it into REVERSE, PARK, back into DRIVE, etc. with no luck, I slipped it into DRIVE, gave it some gas and it "unlocked" so I drove off.

    A few days later on the freeway I noticed a high whining sound that eventually grew louder. At the time I thought that it seemed to correlate with the gas pedal - grew louder when I accelerated, quieter when I backed off the gas a bit. Anyways I turned around and took the truck back to my mechanic.

    He found that something inside the differential had ripped through the case, cutting a long, slot-like hole all the way through. He's said that he's never seen anything like it before - insinuating that I must have been driving the truck recklessly somehow. I'm guessing that when I "unlocked" the truck by giving it gas, that something inside the mis-aligned or otherwise improperly-installed differential actually tore up.

    My question is: What was "locked up" to begin with? (It seems to me that it was an issue with the installation.) and Should he be replacing the part (yet again) at his cost?

    This is the second differential installed by this mechanic that has in some way failed.

    IMG_0837.jpg IMG_0835.jpg
  2. zebra308

    zebra308 Rockstar

    I've never seen anything like this either. I'm interested in finding out what caused that gash. Seems like something was caught in the ring gear?
  3. Dantheman96

    Dantheman96 Member

    Ouch that sucks. I hate to say it but since this will be the 3rd time taking it back to the same mechanic, I would just eat the previous cost and take it to another mechanic who is experienced with setting up rearends. Another option is to go to a salvage yard and pick up a whole rearend with lower miles on it and install it yourself or have it installed. That is what i did when mine went boom and took everything (carrier, spiders, axles) with it. Just remember that a rearend out of a 1/2 ton GM pickup of the same year will not work. It has to be from another Suburban.
  4. JoeM

    JoeM New Member

    Zebra - If I get any more updates or insight (from the mechanic or otherwise), I'll be sure to post. He was going to have the "parts-guy" come and take a look, to see if he'd warranty the part. I'm not holding my breath.

    ---------- Post added at 12:56 PM ---------- Previous post was at 12:54 PM ----------

    Dantheman96 - thanks - I'm thinking that I'll probably end up taking your advice and going elsewhere for the repair. I appreciate the heads-up re: rear-end compatibility!
    Last edited: Feb 3, 2011
  5. kenbarls

    kenbarls New Member

    Sorry to hear that Joe. Will search the solution about it. I am trying to find the answer with those that are experts. I suggest no matter get a used differential it is way cheaper with the same reliability as oem.
    Last edited: Mar 4, 2011
  6. stephan

    stephan Rockstar 4 Years 5000 Posts

    Hey Joe, I've seen this once before. What happend is the spyder pin backed out & ripped the gash in the cover. This is also what locked it up previous to ripping the gash in the cover. The spyder pin is a long steel shaft that goes through the carrier & holds the spyder gears in place between the axle side gears, & the gash in your cover lines up perfectly with where this pin is. This pin is held in place by a bolt. My best guess is that the mechanic either forgot to put the locking bolt in to hold the pin in place & the pin finally fell out, or he put the locking bolt in but forgot to torque it. Either way it's his error & has nothing to do with how you were driving it
  7. 1991 Suburban

    1991 Suburban Rockstar 100 Posts

    I agree completely with Stephan. If it's anything like the work the local mechanic did on my cousin's '98 Dodge, it isn't your fault. On my cousin's, the bolt for the spider pin was broken, and instead of replacing it, the local guy just put the pin in backwards and used it as a wedge against the pin instead of going through it, allowing it to slip enough to hit the case.

    As a second thought, is your rear end a posi unit? (are there springs in the carrier rather than gears?). If it is, there is a chance that a spring came out, and that is what was making the contact. I have seen that one a couple of times, but not bad enough to rip the cover. A friends '64 Chevelle did it pulling out of the gas station once. Completely locked the rear in forward. He had to drive it home in reverse.

    Good luck!

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