01 2500hd .. rear diff cover ??

Discussion in 'General Chevy & GM Tech Questions' started by quicksilver8817, Aug 13, 2012.

  1. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    g80 sorry..

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    What GM says about a friction modifier in the G80..
    ****Important: Installing any friction modifier
    causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality***

    What the Manufacturer of the G80 says...
    ****"From Mr. Ralph Holmquist of Eaton, the maker of the locking differential: "The maintenance schedule for the rear axle was developed by American Axle &Manufacturing and GM truck based on multiple tests. The Eaton locker does not require additional maintenance nor does it add heat to the lube. The lube will darken due to the carbon wear on the clutch surfaces, much the same as a disc brake pad & rotor. This does not damage axle components such as seals or bearings.

    However, a new axle can produce excessive temperatures (plus 350 degrees F) due to the ring & pinion breaking in that will break the lube additives down. Avoid high loads, trailer towing and high speed extended driving during the initial break in of the vehicle.

    After the break in period axle temps will level at a much lower figure. Lube changes are a good idea because the additives are replenished and contaminates such as casting sand are eliminated. The Axle is filled at the Factory with a Synthetic 75/90W GL5 rating made by Texaco under part # 2276.

    The GM Service # is 12378261. This is the only lube we have done extensive testing with to insure locker compatibility. The only negative to using one of these other lubes is an increased potential for clutch chatter. This really doesn't hurt anything and can be corrected by changing the lube. I noticed in the latest GM owners manual the term "or equivalent" when referring to the lube specification. Look for a GL5 rating on the bottle to make sure the ring & pinion, seals & bearings are protected. Limited slip additive is not needed

    "The following information outlines the type of Rear Axle lubrication utilized in GM Truck Axles.
    I. Fluid Type
    II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.
    Last edited: Sep 5, 2012
  3. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    thanks for the reply.. im really set on the one afe offers however everywhere i look it is for the duramax and there is no listing for the vortec .. i think this is because it has the sight glass and it is set to factory fill level but you will be using more fluid because the cover is deeper so idk if there is a difference between the 2500hd vortec 14 bolt rear end and the duramax 14 bolt .. on the website there is a picture and mine is identical to the aa-14-11.5 diff which should fit .. i just wanna know why its not listed for the 6.0 vortec and just for the duramax?
  4. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    how can i identify which diff i have if the tag on the differential is gone ? help please .. i can get a deal on one but have not one clue if it will fit ..
  5. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    Count the bolts.
  6. stchman

    stchman Active Member 2 Years 1000 Posts

    The Proform is about 1/2 the price of other diff covers. I seriously doubt that those bolts will do anything for the bearing caps, but it does have a drain plug!!!!

    Does the 66668 part fit 2013 10 bolt G80 differentials?
  7. jake's silverado

    jake's silverado Epic Member 5+ Years 500 Posts

    Hey folks I think I read (maybe here) that the ribbed for additional cooling was not really true, but more for looks. I still have the original one on my truck. If I had to replace it why would I look at the ribbed vs OE? are they bigger for more oil and thus can I change the oil less frequently? Sorry not meaning to hijack... But why would the OP choose one over the other? I can understand a drain plug, magnetic... but are the Ribbs a big plus?
  8. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    I have the Mag-Hytec covers on the rear axle and the transmission on my 'burb. Came that way from the previous owner.

    You do get more fluid capacity which I see as a plus.

    I would be surprised to learn that the use of an aluminum housing with ribs leads to materially lower internal temperatures.
  9. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    i have the 14 bolt cover.. but i believe there is a 10.5 and 11.5 .. how do i know the difference?
  10. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    I could be mistaken but I believe that the 11.5 is full floating while the 10.5 is semi-floating.

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