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Front and rear diff fluid change

Discussion in 'Maintenance & Upkeep' started by Z-71, Nov 9, 2010.

  1. Z-71

    Z-71 Member

    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
  2. ntbush83

    ntbush83 New Member ROTM Winner 1000 Posts

    Mobil1 or royal purple 75w-90 for the rear. not sure about the front.
  3. Z-71

    Z-71 Member

    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. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts

    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.
  5. ntbush83

    ntbush83 New Member ROTM Winner 1000 Posts

    I have the g80 in mine and I was told to use 80w-90 and that it would be fine.
  6. chevybulldog6

    chevybulldog6 New Member ROTM Winner

    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.
  7. vms4evr

    vms4evr New Member

    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.
  8. silverhobey

    silverhobey Member

    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. vms4evr

    vms4evr New Member

    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. KyleZ71

    KyleZ71 Member ROTM Winner

    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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