Synthetic rear diff and tranny fluids for the G8.

[jboogie]

The G8 is my first "American" car in a while.. I usually change my rear diff and tranny fluids at the same times to a synthetic.

Anyone know what is acceptable to use in our cars?

Thanks.

[Panzer Leader]

Talked with my Tech today on this very subject. He suggested staying with the GM transmission fluid but going with synthetic in the differential (probably RP) the V6 has 2 trans filters, the pan and a solenoid filter. Don't know about the V8s.

[-Ray-]

General Motors DEXRON®-VI Global Service-Fill Specification

During early 2005 General Motors released a newly developed automatic transmission fluid (ATF) for the factory fill of all GM Powertrain stepped gear automatic transmissions. The new fluid provides significantly improved performance in terms of friction durability, viscosity stability, aeration and foam control and oxidation resistance. In addition, the fluid has the potential to enable improved fuel economy and extended drain intervals. Since the performance of the new fluid far exceeded that of the DEXRON®-III service-fill fluids available at the time it became necessary to upgrade the DEXRON® service-fill specification in order to ensure that similar fluids were available in the market for service situations. This latest upgrade to the service- fill specification is designated DEXRON®-VI.
Since General Motors introduced the first ATF service-fill specification in 1949 it has been periodically necessary to upgrade the specification. This upgrading process ensures that available service fill fluids are of an appropriate quality for use in transmissions that have been designed around the factory fill fluid performance. It should be noted that, as with previous upgrades, DEXRON®-VI fluids are designed to be backward compatible with earlier transmission hardware. More importantly, earlier type fluids are not forward compatible with transmission hardware that was designed to use DEXRON®-VI fluid, i.e. DEXRON®-III is not compatible with the most recently designed transmissions, and the use of these earlier type fluids could result in transmission damage. All current calibrations and certification tests are now conducted with DEXRON®-VI ATF. DEXRON®-III fluids should not be used for these applications where the owners manual recommends the use of DEXRON®-VI. GM does not license or support obsolete ATF specifications or the use of fluids that are being marketed against cancelled specifications.
All DEXRON®-III licenses expire at the end of 2006 and will not be renewed. Beyond that date GM will only support the use of DEXRON®-VI fluids for use in Hydra-Matic transmissions. Fluids sold in the market after that date bearing claims such as “suitable for use in DEXRON®-III applications” or similar wording should be avoided. DEXRON®-VI licensed fluids are fully backward compatible and can be used in all applications covered by earlier GM ATF specifications.
The use of unlicensed fluids and/or non GM approved aftermarket additives may prove detrimental to transmission performance and void warranty coverage.
There is a published list of GM-approved brands of DEXRON®-VI (see page two of this release). This list represents the companies who have conducted the appropriate testing and received GM approval. Company name, license number, and brand name are shown. This list will be updated on a regular basis as more approved products are added.

[Chewy]

What Ray said! VI is the BOMB! No need to replace for a while unless you're racing it ALL THE TIME.

[-Ray-]

I didn't say that, I copied GM's document. LOL

[jboogie]

So the DEXRON VI is a must in the tranny. Good to know.

Can i put Redline or Amsoil in the rear diff?

[american_kestrel]

I asked questions about this too. Found some good info from others smarter on the subject. Basically requires a specific blend of "carbon friction modifier" added to differential fluid. Since the required percentage must be very close to the stock GM fluid....best to just buy the GM part #. Can find it a number of places a little cheaper than dealership, still with the GM logo on the bottle.

Check out one of this site/forum sponsors authorized to advertise here.

Great experience with Greg from Pace Performance.....good price on the differential fluid you need.

http://forum.grrrr8.net/forumdisplay.php?f=94

[Sephiroth]

Dexron VI is a synthetic specification anyway, and so is the stock GM LSD fluid too. There's absolutely no reason to use any other rear diff fluid, and as Kestrel mentioned, I would be worried about the friction modifyers any other fluid had anyway. Who knows if it's the right kind, or the right amount.

[texn884]

When the time comes I am goign to put Royal Purple in the Tranny and Rear End. I have it in the engine and so far so gooooood.

[AVIDMOTION]

Is Amsoil on the favored list for synthetic trans fluid? EAST COAST SUPERCHARGING in Cream ridge NJ has a trans fluid exchange and uses Amsoil trans fluid for 129 bucks. I wanted to do this.