99 Sierra Transfer Case And Differential Fluids

[scott0303]

I am going to change the transfer case and both differential fluids in my 99 Sierra 4 wheel drive truck. Does anyone have any advice on what is best to use when replacing them?

[twavor]

Synthetic 75w-90 in the rear and regular ole' 80w-90 in the front. Need to know what transfer case you have to know what fluid to put in it. T-case with auto 4x4 requires Auto-Trac II fluid (available only from your local GM dealer, apparently) and pretty much every other t-case will use good ol' Dexron III.

 

Travis

[Black02Silverado]

Scott,

 

Travis pretty much covered it. You can go with a synthetic in the front differential if you want, it is an option. The rear came from the factory with synthetic and is required.

 

You will need 2 qts for the front diff and the rear will take a little over 2 qts so if you got all the same fluild you would need 5qts total to do the front and rear. The T-case takes 2qts.

[scott0303]

Synthetic 75w-90 in the rear and regular ole' 80w-90 in the front. Need to know what transfer case you have to know what fluid to put in it. T-case with auto 4x4 requires Auto-Trac II fluid (available only from your local GM dealer, apparently) and pretty much every other t-case will use good ol' Dexron III.

 

Travis

 

Not sure what you mean by auto 4x4? Are you saying if it has an automatic transmission? If not, how can I tell which I have? thx

[twavor]

You can crawl under the truck and check out the round tag on the transfer case to see what model it is to be sure. Do you have a the stick on the floor or do you have a push button switch to engage 4x4? Does the pushbuttons include a round button that says 'Auto 4wd'?

 

Travis

[scott0303]

You can crawl under the truck and check out the round tag on the transfer case to see what model it is to be sure. Do you have a the stick on the floor or do you have a push button switch to engage 4x4? Does the pushbuttons include a round button that says 'Auto 4wd'?

 

Travis

 

 

No button. I have to manually shift into 4 wheel drive. Thx

[twavor]

You can crawl under the truck and check out the round tag on the transfer case to see what model it is to be sure. Do you have a the stick on the floor or do you have a push button switch to engage 4x4? Does the pushbuttons include a round button that says 'Auto 4wd'?

 

Travis

 

 

No button. I have to manually shift into 4 wheel drive. Thx

 

Awesome....wish mine was that way! Anyway, all you need is some good ol' Dexron III to fill your transfer case.

 

Travis

[Black02Silverado]

You can crawl under the truck and check out the round tag on the transfer case to see what model it is to be sure. Do you have a the stick on the floor or do you have a push button switch to engage 4x4? Does the pushbuttons include a round button that says 'Auto 4wd'?

 

Travis

 

 

No button. I have to manually shift into 4 wheel drive. Thx

 

 

 

Then you will need Dexron III fluid for your transfer case.

[scott0303]

Thanks for everyones help!

 

So do you all use a particular brand like Mobil1 synthetic or something else?

[scott0303]

Scott,

 

Travis pretty much covered it. You can go with a synthetic in the front differential if you want, it is an option. The rear came from the factory with synthetic and is required.

 

You will need 2 qts for the front diff and the rear will take a little over 2 qts so if you got all the same fluild you would need 5qts total to do the front and rear. The T-case takes 2qts.

 

 

So if I used synthetic in the front as well, would I go with the 75w-90 or 80w-90? thx

[Black02Silverado]

Thanks for everyones help!

 

So do you all use a particular brand like Mobil1 synthetic or something else?

 

Mobil 1, AMSOIL, Royal Purple and Redline are the most common synthetic gear oils. If you are interested in AMSOIL, PM me your address and I can send you a total price delivered to your door.

 

 

So if I used synthetic in the front as well, would I go with the 75w-90 or 80w-90? thx

 

I would go with 75w-90 for both. That way you only have to worry about one grade lubricant.

[scott0303]

Guys, are there any additives that I need to put in besides the synthetic? Was reading somewhere online about needing to put a posi additive in some rear ends but it wasnt very specific as to which GM trucks. Thx

[Black02Silverado]

Guys, are there any additives that I need to put in besides the synthetic? Was reading somewhere online about needing to put a posi additive in some rear ends but it wasnt very specific as to which GM trucks. Thx

 

 

You do not need any additive for your truck. Just change out the fluid and all will be fine.

[scott0303]

So far I have done the rear diff. Oil looked pretty good, didnt see much as far as any metal shavings. The front was a different story. Oil looked really bad and old. Quite a few shavings on the magnet. Must have been the original oil. Keep in mind that I am the 3rd owner of this truck. Its got 128,000 on it. Tomorrow I am going to do the transfer case.