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The G80 good or bad?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by stchman, Dec 5, 2012.

  1. stchman

    stchman New Member 1000 Posts

    Doing a little reading, and there are a lot of people that slam on the G80 saying that they explode all the time.

    I had a G80 in the 1998 W/T, my 2008 Silverado, and now in my 2013 Silverado. No problems whatsoever.

    IMO, if they were so bad, GM would not be putting 100K power train warranties on them.

    Any thoughts?
  2. j cat

    j cat Active Member 1000 Posts

    I have the G80 diff since 2000. the diff requires a breaking period of about 2,ooomi. during this time no heavy tow/hauling. the gear teeth need to go Thu this breaking in with light loads. then the diff oil requires replacing and the cover need be removed for cleaning and inspection for proper wear marks .

    most owners are not informed of these requirements . my guess is it would devalue the vehicle with more repair/maintenance requirements than a competitor.

    the diff cover must be removed and the box cleaned every 40,ooomi so that the locking portion moves smoothly to engage with NO Slaming engagement. I use mineral spirits/low odor paint thinner to clean out the box.

    I found when new quite a bit of debris created with this breakin . now 140,ooomi . stays clean, operates smoothly.

    If this diff pulls heavy loads when new the teeth get so hot that the metal gets brittle , then the teeth crack and fall of and its all over. the high box heat makes the gear oil burn up . the gear oil must be replaced @2,ooomi because even with light loads the oil gets hotter than normal. also the metal material need be cleaned out.
  3. stchman

    stchman New Member 1000 Posts

    I've looked at my owner's manual and it does not state that the rear axle fluid needs changing. Where did you get this information?

    Thanks.
  4. RayVoy

    RayVoy Active Member 1000 Posts

    He's my 2 cents: I feel the G80 and the 4AWD position of the t-case fall into the same category. Both have mechanical actuation that causes a spinning wheel(s) to "BANG" into a non-spinning wheel(s). With vehicles as heavy as the full-size trucks, that is a lot of energy resistance. If your foot is in it and the coupling takes place with a heavy jarring something is going to break. If you can get off the gas when you feel the wheel(s) slip, the jarring may not be as bad.

    I'm a big fan of the G80, not so of the 4AWD.
  5. stchman

    stchman New Member 1000 Posts

    The G80 is designed for only low speed locking (getting out of a ditch), not as a racing differential.
  6. RayVoy

    RayVoy Active Member 1000 Posts

    I know that, don't believe I said anything about racing.

    I'm talking about the guy who thinks the way to get out of a slippery/icy ditch is with a heavy right foot.
  7. stchman

    stchman New Member 1000 Posts

    Agreed, when you are slipping, simply give it a little gas to lock the axle.
  8. RayVoy

    RayVoy Active Member 1000 Posts

    No, that is not what I'm saying; it will do that automatically, as soon as the rear wheel speed sensors detect a difference in rpms.

    What I'm saying is, let's say one rear wheel is on pavement and the other is in mud/snow/ice. The G80 has some posi-trac clutches, but for the most part acts like an open diff when it is not locked. The open diff would let the wheel with the least traction spin. The G80 has a pawl that mechanically locks both sides of the diff when the difference in wheel speed exceeds 100 rpm.

    All I'm saying, is if you know there is a possibility of wheel spin and you gently apply the gas, there will still be a jarring when the sides lock; but, it will not be as severe as the jar when the sides lock under WOT. A WOT lock will break something eventually.
  9. j cat

    j cat Active Member 1000 Posts

    the manual says nothing . I got all my info from the manufacturer , and my own work on these. then all the forum info from other owners / repairers with these.

    if the rear diff is banging in the box needs cleaning and fluid replacement with the proper synthetic gear lube.

    only using the drain plug when replacing fluid is not the proper proceedure. the box must be cleaned and the magnet on the cover .

    my vehicle used to bang in then I searched and got these answers to whats up. that was years ago. same box not banging now , because of what I do and learned.
  10. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    IMHO there's nothing wrong with a G80 for typical truck-owner uses, which is why my truck still has its G80. Mud bogging and monster trucking is NOT, however, what it was built for ... and the people who tend to slam the G80's tend to be extremists (at least from what I've read) doing such things.

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