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Thread: Rear Diff service tips?

  1. #1
    Join Date
    Sep 2006
    Location
    Iowa (central)
    Posts
    148

    Default Rear Diff service tips?

    I'm getting ready to do a rear diff service. I am going to drain and refill with synthetic, but what else needs to be done? Looks like a simple job, but I am along way from being a poor mechanic, and simple tends to get complex in a hurry for me. When I put the cover back on, what do I torque the bolts to? What about the front diff? Is it time for that when I do the rear diff? Does any one know off hand what the quantities the two diffs hold? Any tips, tricks or advice would be very much appriciated!
    Shed
    01' LB7 2500 HD ext.cab, auto, 4" magnaflow, airaid intake, Mag-Hytec tranny pan, all Amsoil, Bilsteins.

    In pusuit of the perfect camper pulling rig....

    05'-30' Pilgrim 5th wheel

    Always on the road headin for a campsite!

  2. #2
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    Drain/refill. Nothing more to do, short of an overhaul (or overkill). DO NOT remove the cover. It has a drain plug in the bottom (3/8" square slot, and magnetized). Drain when hot on a level surface for the best results. Refill with 75w-90 synthetic (Or 75w-140, if towing heavy/often in hot climate. You may be a candidate if full time RV'ing).

    Rear diff: Just shy of 4 qts. Fill to about 1/2" below the fill hole. Check the vent tube while you are there. It must not be kinked, or have any loops or dips in it (no place for oil to collect).

    Front diff: 2 qts. Also check the vent tube. Use the same lube as the rear.

    Transfer case: 2 qts. Dexron III ATF.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
    Join Date
    Sep 2006
    Location
    Iowa (central)
    Posts
    148

    Default

    Mav, Once again thank you for your knowledge and advice! I did not even think about the transfer case (duh). Is there a drain and filler on it also?
    Shed
    01' LB7 2500 HD ext.cab, auto, 4" magnaflow, airaid intake, Mag-Hytec tranny pan, all Amsoil, Bilsteins.

    In pusuit of the perfect camper pulling rig....

    05'-30' Pilgrim 5th wheel

    Always on the road headin for a campsite!

  4. #4
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    I didn't know if you omitted the TC on purpose or not, so I threw it in (since it is one of the most neglected service points). Fill it to about the fill hole, which should be about 2 qts.

    It has drain/fill plugs (at the rear, just to the left of the rear output). The case and plugs are magnesium, so great care should be taken to R/R. When loosening, "rock" it back and forth as you remove it (like you would to tap threads) until it's just about finger-loose. If not, it can grab threads and take them out with the plug. Doesn't happen often, but it can. To install, be sure the plug is well lubricated, preferably with a "silver type" anti-seize. Do not overtighten, as it will just keep on going, even though it has tapered threads.

    Just FYI:
    I did a bumper to bumper service on a friend's 2004 LB7 4x4 yesterday. It has 96K on it, and the only service that had been done since new was the engine oil, and a fuel filter change about 25K ago (that he knew of, since he bought it new about 50K ago). Everything was UGLY! But it's a happy truck, now.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  5. #5
    Join Date
    May 2008
    Location
    Springville, CA
    Posts
    73

    Default

    Quote Originally Posted by DmaxMaverick View Post
    I did a bumper to bumper service on a friend's 2004 LB7 4x4 yesterday. It has 96K on it, and the only service that had been done since new was the engine oil, and a fuel filter change about 25K ago (that he knew of, since he bought it new about 50K ago). Everything was UGLY! But it's a happy truck, now.
    Yeah, Baby!

    Sure do appreciate your help with that!!! New fluids, new tires, a couple of new glow plugs on their way. Looking for a new belt and tensioner and she's going to be real happy. . .
    '04 GMC 2500HD LB7 CC SB 4x4, 265/75R17 Dueler Revo, Bilstein HD, Banks Ram-Air, Edge Juice w/Attitude, free-flowing quiet exhaust on the cheap

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