Put some RedLine fluid in the diff of our "new" 245K mile E300D. Now it has a pretty good "whine".

Backlash is the typical put it in drive and clunk goes the rear end with this 95.

Dont beleive the 95 called for synth gear oil. Thinking of swapping back dino 90w but...first

does this whine indicate too much wear, or is is simply a function of the lighter synth fluid and a loosely set up ring/pinion? Meaning, is it critical I put heavier lube back in? Or can I let it "sing" thru the colder winter?

I've had the clunk before, in almost all the 300s I've owned, but never such whine from the R&P.