I understand GM now has a differential lubricant for Corvette limited slip rear ends.

Supposedly, this was changed last March in my vehicle, as I 'complained' that the rear end 'clunked' backing out of my garage.

After the fluid replacement, the 'clunk' became increasingly loud, and started to sound and feel as if the rear end was going to fall out.

The local Chevrolet dealer is willing to check it out, but with a $120 diagnosis fee, even though Chevrolet Customer Service has requested the inspection.

As I worked as a wrench all my life, I know who the good wrenches are here in Reno, and the best is a good friend of mine who I worked next to at Chevrolet for 5 years before he and I left for other endeavors. He now owns a nice auto repair facility, that I have donated a multitude of tools to, as I can no longer wrench, even on my own cars.

Long story short, we took a sampler of the diff fluid, which I sent off to Blackstone Labs for analysis and we put in a tube of friction modifier.

Lo and behold, 99% of the noise went away when cold, completely gone when warm.

Now, the dealer tells me that adding the friction modifier to the differential, with GM's new all inclusive differential lube, will destroy the clutches in my C6's Limited Slip rear end.

This does not ring true to me. However, what better a resource to verify this as nonsense or truth, than right here in the forum!

So...What say you? Comments anyone?!!

Joe
2006, C6 Base Coupe

 

I'm no expert, but I'm going to call bullshit on that one. How would additional friction modifier destroy your diff clutches? If anything, I would think that the clutches may slip a bit easier with the additional FM in there, due to increased lubricity. How, pray tell, would that destroy your clutches? Most likely, they put the wrong oil in the first place. Dealers can really be so FOS.

 

This is the fluid for your car. No additives required. This fluid has resolved a lot of diff noises on this forum. Some have even filled with high end aftermarket fluids that have not fixed their problems and the noises finally went away after draining and re-filling with this fluid.

 

Here's the official GM stance on the Dexron LS rear diff fluid. Simply put, don't add anything else to the fluid, the friction modifier is already in there.

Also from: Rear Axle Clunk and/or Chatter Type Noise on Turns
(Drain/Refill Rear Differential Fluid) #07-04-20-002B

Important: DO NOT add any limited-slip additive (friction modifier). With this new fluid (Dexron LS Gear Oil 75W-90) it is no longer required to add friction modifier. If friction modifier is added, it will cause the fluid to lose some of it's friction reducing properties as well as reducing seal life.

 

CORRECT INFORMATION HERE

and to those who question the detriments of adding extra friction modifier to the lube it may NOT be compatible with the material composition of the seals, yes they all are not just "rubber" and it may also impact the adhesives that bond the friction material of the plates to the metal backing plates..................

work in the axle and differential business................