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  1. #1

    Question Front and rear diff fluid change

    I am getting the truck ready for winter and need to change the front and rear diff fluid.I have checked my manual to get the part numbers but they don't work.I have also tried running some searches but I guess my searching skills are weak because I can't find anything.I need to know what the correct fluid to put in the rear diff on a 03 silverado with the g-80 govlock.And also the front...I'm pretty sure they are different.Thanks


    03 Chevy Silverado 1500 ext cab Z-71
    79 AMC Spirit GT
    77 Olds cutlass supreme

  2. #2

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    Mobil1 or royal purple 75w-90 for the rear. not sure about the front.

    2006 Duramax LBZ
    Edge Evo
    4'' Diamond eye to 6'' tip
    16'' ion alloy, 33'' fierce attitudes
    Lots of work left to do!

  3. #3

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    okay.The manual says 75w-90 for the rear and 80w-90 for the front...but I didn't know if it needed to be something specific or the actual gm stuff being that it's the locker axle.

  4. #4

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    You need to also use a special lubricant for lockers. I forget what it's called, but it's in a fairly large tube next to the gear oil at Autozone. The clutch packs in the locker need special lube, but you also put in regular gear oil.
    Christopher

    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



    There are 10 kinds of people, those who understand binary, and those who dont...

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  5. #5

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    I have the g80 in mine and I was told to use 80w-90 and that it would be fine.

  6. #6

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    80w-90 in the front and 75w-90 in the rear with a specific additive. The specific lubricant for the rear axle is just a synthetic fluid to mix with a non synthetic gear oil. So after talking to a bunch of people, they suggested I just use a synthetic gear oil and I have had no issues since I did it starting about 25K miles ago...hope this will help.
    2005 Chevy Silverado 1500 Z71 Crew Cab
    8in ProComp Suspension Lift, 4in Shackle Flip Kit, 3in Performance Products Body Lift, 17x9 Moto Metal wheels, 35x12.50x17 ProComp Xterrains, K&N cold air intake kit, Custom 3in exhaust, GoRhrino Black spring loaded steps, Truxedo Bed Cover, "SS" style Instrument Cluster with blue pointers and Trans Temp Gauge, JVC indash touchscreen DVD player, 2 MTX 10in subwoofers, Sony Xplode 1000watt amp, Radio Shack CB with dual black whips, Optima yellow top battery

  7. #7

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    Quote Originally Posted by ntbush83 View Post
    Mobil1 or royal purple 75w-90 for the rear. not sure about the front.
    This will be fine front and rear. The synthetic diff fluid will work over a big temperature range and actually simulate more than 75w-90 range. It works fine. That is what I'm running. In the rear diff with limited slip there is an additive that you need if you run dino gear oil. Mobil 1 Synthetic also says add it. As noted it helps with the clutch packs in the posi unit. You'll find it with the diff fluid at Napa and Autozone (that I know of) for about $8. It's in a tube and the stuff looks blue. If you use RP or RedLine synthetic diff fluid then you don't need the additive.

    An easy to tell if you need additive. Swap out with the new synthetic fluid. Go drive the truck in a parking lot in slow tight circles both left and right. This packs the fluid into all the spots in the diff. If you hear any noise from the diff then you need the limited slip additive. Or just throw it in. Worst case it is a waste of $8. It won't hurt anything if your diff doesn't need it.

    The only weird fluid you need from the dealer is the stuff in the transfer case. That is also some weird blue looking stuff that looks like tranny fluid. It's about $20 a bottle and you need 2 bottles if I remember right.

    Changing those fluids is part of your 50K maintenance work.
    2006 Chevy Silverado, 5.3L, Z71, Extended Cab. Tow Mule.
    2002 Chevy Corvette Z06, 5.7L, Slightly Modded. Tow Payload.
    2005 Craftsman Riding Mower, 17hp, light mods.

  8. #8
    Master Mechanic silverhobey's Avatar
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    Quote Originally Posted by vms4evr View Post
    This will be fine front and rear. The synthetic diff fluid will work over a big temperature range and actually simulate more than 75w-90 range. It works fine. That is what I'm running. In the rear diff with limited slip there is an additive that you need if you run dino gear oil. Mobil 1 Synthetic also says add it. As noted it helps with the clutch packs in the posi unit. You'll find it with the diff fluid at Napa and Autozone (that I know of) for about $8. It's in a tube and the stuff looks blue. If you use RP or RedLine synthetic diff fluid then you don't need the additive.

    An easy to tell if you need additive. Swap out with the new synthetic fluid. Go drive the truck in a parking lot in slow tight circles both left and right. This packs the fluid into all the spots in the diff. If you hear any noise from the diff then you need the limited slip additive. Or just throw it in. Worst case it is a waste of $8. It won't hurt anything if your diff doesn't need it.

    The only weird fluid you need from the dealer is the stuff in the transfer case. That is also some weird blue looking stuff that looks like tranny fluid. It's about $20 a bottle and you need 2 bottles if I remember right.

    Changing those fluids is part of your 50K maintenance work.
    I see you have lots of info on the fluid changes, just wonder if you maintain the Mower with Mods----that's hilarious that you have that as one of your vehicles----Great idea, as I know I would list it too if I had one.

  9. #9

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    Thanks Hobey. Yeah I had to add the riding mower since it has mods too! I changed all the fluids on the truck. Other than the transfer case I use the same fluids I use on the Z06. The Vette is part street and part track, road course racing. I change fluids in it all the time. I am very familiar with fluids and what works for me. I run the Royal Purple stuff from end to end in the Vette. Now the truck. I should buy stock in them or Mobil 1. I go through the stuff often enough... The riding mower and the Celica get the used oil from the Vette. I do my part and recycle.... LOL

  10. #10
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    Im at college (so I have no where to to do it) and there's a local chevy dealership with a goodwrench service station down the road. How much would it run me if I had them change the fluids in my 03 Silverado Z71?

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