I replaced my rear diff with AMSOIL Severe Gear 75W-90. Love the stuff!

 

How often you change your diff fluid is dependent on how you drive your car, level of modifications, and level of comfort. If you are tracking your car you need to change it much more often than if it is a daily driver.

IMO there is no such thing as a lifetime fluid. Assuming normal usage I would change both the Transmission fluid and Diff fluid every 50k-60k miles. A number of the MB guys have had issues with their transmissions at a 100k+ miles after not changing the fluid.

Think of the fluids as the life blood of your car. 3, 4, 5 transmission fluid changes are a lot cheaper than replacing the transmission.

I am being a bit excessive in my diff fluid changes but I have done it every ~20k miles. The qualifier being that I had a Phantom Grip installed and recently wanted it inspected. After trips to the Drag Strip and Road Atlanta the PG still looks like new. I think the PG is much better than some people give it credit for but if the WaveTrack had been an option when I got the PG it would have been a no brainer. The WaveTrack all the way.

 

A few things I'll throw in here since I did replace the differential fluid in my C55 AMG earlier this year before I totaled it . I did a fair amount of research on this on MBWorld.org Mercedes Benz Enthusiast Community and as others have mentioned, although Mercedes-Benz maintenance guides do tend to either (a) neglect to mention differential fluid change as part of regular maintenance, or (b) state that it is maintenance free and does not need to be changed, many enthusiasts opt for the safe route and I knew many C32/C55 owners who insisted 40,000 mile intervals was a good rate at which to swap the diffy fluid.

That being said, I took this advice and went ahead and drained and refilled by C55 AMG differential and when the fluid came out it looked really clean actually! Still hadn't lost its synthetic clear color.

A few things to be careful about.

(1) I don't think anyone here has actually mentioned the OEM recommended differential fluid viscosity. The MB recommended for the C55 was 1.5L of Hypoid Gear Oil 85w-90. I actually bought the Mercedes brand at $32 a liter to be safe. It very well could be different for the SRT-6 or Limited, but all I am saying is just don't go out to Advance Auto Parts and buy the first synthetic gear oil you see. In doing research I found a thread in which a guy filled his differential with the wrong fluid and it turned to molasses once he started driving around killing his gas mileage. Needless to say, he had a heck of a time getting it all out!

(2) Here were the tools I used to change the fluid:

1.5 L Hypoid gear oil 85w-90 (bought two quarts from autohausaz MB brand for $58)*
14 mm hex socket
Breaker bar (optional but I bought one out of precaution, the filler and drain bolts are hard to get off)
Liquid transfer pump (to fill diff.)
Good jack stands or ramps (car needs to be level)

(3) For some more good reading check this thread out: Differential fluid change DIY? - MBWorld.org Forums

Anyone know what the OEM spec viscosity is for the Crossfire differential?

 

From the SRT6 service manual:

DESCRIPTION - DIFFERENTIAL LUBRICANT

Note: Refer to the Owner’s Manual for the recommended differential lubricant change intervals for this axle.

Use synthetic SAE 75W-85 axle lubricant that meets MB 231.1, such as Mopar 05126035AA. An SAE 80W-90 GL-5/MIL-2105-E Synthetic Axle Lubricant may be substituted. Reduced axle durability may result if an unapproved product is used.


I looked through the owner's manual and it does not state any change interval.

EDIT: Fluid capacity: 1.3 L (1.4 qts.)

 

Wow, welcome back Chuck! You haven't posted in awhile. Hope to see you on Sunday!

 

Thumper, thank you! Now if you could just provide the specified amount of fluid required... I know I know you have already done enough! Anyone else?

 

You know, I was going to put it my original post but got distracted looking for the service change interval

Here you go: 1.3 L (1.4 qts.)

 

Awesome! Thank you!

 

Royal Purple - GL4 and GL5 - 75w90 Max Gear.
Thoughts on using this?

 

Thanks for all the responses but went to autohausaz and could not find the lubricant mentioned.