synthetic trans and rear diff fluids

PELICAN · July 30, 2005

I have over 93,000 miles on my truck and thinking on the next oil change I am going to switch to synthetic in the transmission and rear diff since I am already running synthetic oil. Does anybody else run synthetics in thier trans. and rear diff. and if so what brand?

bigdogs · July 30, 2005

I have synthetic diff fluids, the grape juice in the front and Amsoil Series 2K in the rear. In the Allison I still have the factory fluid but when it comes time to change at like 25K I would like to flush that (if I can find a place that will do it) and refill with synthetic, either the Amsoil stuff made especially for Allison's or the TranSynd.

rjirvine · July 31, 2005

My 2000 Silverado ext cab with a 5.7 and non-locking rear axle had 92k miles on it when i changed my fluids. I used GM 75W-90 for front and rear differentials, and Autotrak II for the transfer case. The fluid from the dealer was spendy at about $26/qt, but I figure if I only have to do it every 100k or so it's not too bad.

mcreyaufmiller · August 1, 2005

I use royal purple in my rear, and standard fluid in the tranny. I use Mobil 1 in the crankcase.

BADGERMAN · August 1, 2005

I run Royal Purple in everything

gcook · August 1, 2005

I have a 2002 Z71 with a noisy front differential. I changed the fluid and went with Amsoil Severe Gear 75W 90. Really reduced the noise from the diff.

JACKFAVOR · August 8, 2005

I have a 2002 Z71 with a noisy front differential. I changed the fluid and went with Amsoil Severe Gear 75W 90. Really reduced the noise from the diff.

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AMSOIL in everything but the transfer case autotrac II there.

496 CUBIC INCHES · August 8, 2005

I've got M1 75w-90 in the front diff,Royal Purple max-gear 75w-90 in the rear diff,M1 ATF in the Allison and transfer-case. The engine has M1 in it as well.

I like M1 products as they are reasonably priced,easy to find and are some of the best synthetics on the market. I have Royal Purple in the rear diff because I couldn't find enough M1 to do both diffs,and I sure as hell wasn't going to spend close to $30 for GMs synthetic.

JBZ71 · August 8, 2005

M1 in everything..

01silverado2500 · August 8, 2005

Did the 2005s come with synthetic gear oil from the factory?

It says on the window sticker "Long Life Rear Axle fluid"

I plan on runin Mobil 1 once its broke in, would it be worth it to change out the other fluids to synthetic also?

Supercop8100 · August 9, 2005

Royal Purple synthetic in everything. Even Purple Ice in the radiator. Great stuff.

bigdogs · August 10, 2005

Did the 2005s come with synthetic gear oil from the factory?

It says on the window sticker "Long Life Rear Axle fluid"

I plan on runin Mobil 1 once its broke in, would it be worth it to change out the other fluids to synthetic also?

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I know my 2003 Sierra 2500HD came with it in the rear which I changed after the break in to Amsoil Series 2K. The front came with regular gear oil but was replaced under a TSB to the grape juice

Tahoe2 · March 10, 2006

Mobil 1 .....IN....Motor, Tranny & Diff.

rfingtrk00 · March 10, 2006

Mobil in engine trani and diff. I put synthitic in my diff with my Auburn pro and it started binding bad after awhile. Went back to dino oil with additive binding gone. Didnt realize it made that big of a diffrence