datadock

I have developed a whine in my rear end when decelerating. It sounds somewhat like a bearing going bad. A friend suggested that changing the differential fluid would probably eliminate the whine. My service manual says to only use a synthetic lubricant that meets GM spec 9986115, plus 4 ounces of a limited slip differential lubricant additive. I have read a lot of internet posts on alternative synthetic lubricants, but none of them seem to meet the GM spec (Amsoil, Royal Purple, Mobil1, etc.) There is a lot of conflicting opinion as to whether it is safe to use a non-GM spec lubricant. Does anyone have a recommendation based upon experience as to what lubricants can be used in the Z06 differential? Also, if other brands are acceptable, do they require the friction modifier additive?

dbaker

I've run the Amsoil SG 75-90 in the diff of my 02Z for years.Good stuff.

http://www.amsoil.com/MyGarage/Vehic...LET+CORVETTE+S

\db2
carolina

BlueFish81

I have Royal Purple 75W90 in my 575RWHP 04Z for the past 2500 miles with great results. While I changed the rear fluid I also changed the transmission fluid to Royal Purple ATF and the shifts have gotten much smoother. I also had done the same to my 08 C6 with the same great results.

Karn

datadock

Did either of you use the 4oz of additive that GM recommends with their differential fluid? I have heard that it is not needed with some of the non-GM synthetics.

81c3

RP in mine also. No additive need with RP

BlueFish81

Not needed.

Bills Z06

I use Amsoil 75W-90. Amsoil says the additive is not necessary, but I use it anyway. No issues!

halp

How about Mobil 1 Synthetic gear lube LS 75 W 90?
It has the limited slip additive in it.

l2vette

Try using the GM sythetic rear axel fluid that contains the limited slip additive. It's the factory fill on all C6's.

Omaha02Z06

Thanks for posting that link on where to buy Amsoil. I use Royal Purple fluids now and am not happy with how it acts in the tranny when cold. Going to switch to Amsoil fluids for the tranny and rear diff.

Carnac

I am sure that Royal Purple, Amsoil, Mobil 1, Red Line, etc are all excellent and probably better than the GM, however none of the above submitted their products for GM certification (at least that I can find).

Since I still have a warranty in effect, I went with the GM tranny and rear diff fluid. The price was reasonable. Be sure to get the correct tranny fluid for the Z06. GM went to a new fluid for most of its cars, but for the Z06 the latest (Dex VI) was recommended for a short time and then changed back to the older GM part # with the warrning of possible transmission failure with the newer fluid. If you go decide to use the OEM GM fluid, make your parts guy look it up, not just hand you the same part # used on other cars.

The change itself was straight forward, but you will want to look in the DYI sticky - there is a good write-up with pictures. There are a couple of "got yahs".

Cheers - Jim

ps - I have been very happy with my limited slip and tranny feel using the OEM fluids...

Toque

I recently put in Amsoil, and am happy so far. I have only heard good things.

I also wrote a procedure on the fluid change if you want to know how to do it.
http://mysite.verizon.net/res0aae8/diff.html

Toque

dbaker

Send me an email and I can save you some $ on Amsoil products.

\db2
carolina

C66 Racing

For those considering AMSOIL, please drop me a PM so I can ensure you get dealer wholesale pricing, about 25% below retail, via the AMSOIL Preferred Customer Program.

As an FYI, this is the fluid that AMSOIL recommends for the C5 Z06 and what I've been running in my diff since the 04 season (no failures to date).
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (Product Code SVGQT)

As was mentioned above, this fluid comes with friction modifier already in it and adding extra additive is not normally needed for the C5 Z06 (and I don't run extra in mine). Some, like Toque above, chose to run a little extra additive, such as the AMSOIL Slip-Lock Differential Additive (Product Code ADATB) to absolutely ensure they don't get diff chatter, or to pick up a tube of the Slip Lock and have it handy if the diff does chatter. This tube comes with a long tip and could easily be used to squirt in an ounce or two to the diff fill plug without draining the diff.

johnnytaboo

FWIW I recently switched to Amsoil, and I'm very happy. Subdriver's hooked me up a couple times now, and Toques step by step how-to is very easy to follow.