rear differential fluid change
 

I have a 2001 Silverado 1500 LS 2wd 5.3L and I'm getting ready to change the differential fluid. I want to put synthetic fluid in when I do the change. What is the best fluid that you guys recommend. Also, is anybody aware of the fluid capacity of the rear diff. of my truck. Thanks in advance for the help!

i just did my front an rear diff last month. I went with Royal Purple its not cheap but you know it will hold up to anything you throw at it. To be safe i bought 3qts because it uses 2.25qts. 75w90 is what they recommend but that was just 60 bucks for the rear. Make use you loosen the fill plug first so you can re-fill b4 you take off the drain plug or diff cover. Have a 5/8s alan wrench handy so you can stick in the fill hole to check the fluid level. Once the tip of the wrench is wet ur golden.

Thanks for the reply. From what I can understand most of the gear oils available have the limited slip additive that aren't ideal when used in a truck. I've been considering either Royal Purple or Amsoil sever gear. What did you do about replacing the rear axle housing gasket?

I've run both royal purple and amsoil, no problems with either.
If you have a limited slip and it calls for an additive I believe you'll still need to add some. Some of the newer diffs have a drain plug in the bottom of the housing and you don't have to pull the cover. That is how my '00 is but it has a 10.5" full floating axle.

I checked my glove box and found the code gt4 for my differential, which I believe isn't the locking differential. So at this point I guess I can safely add the limited slip additive. I will probably pull the cover anyway as my truck has about 150k on it and I want to clean it out in there.

Thanks

GT4 is the axle ratio which is 3.73 and G80 is limited slip.
Since you don't have G80 you don't have to worry about adding the additive.

No additive in rear diff. Camaro and vetts are the only ones that get additive.

I had to add the additive to my 10.5" rear axle due to clutch chatter on turns. Severe slip-stick going on that felt like it was gonna break an axle shaft when loaded on turns.

Now I'm confused. I thought the g80 didn't get the additive because it is the locking diff and all the other ones are considered to be limited slip and require the ls additive.

If you look in the Gm service manuals they don't mention adding additive on refill of differential for trucks. Camaro and Corvette they are specific on adding additive.