PSA on differential (gear) oil

After using standard Valvoline

$28 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 with the friction modifier ever since I got my 05 in 05, I decided to try full synthetic 75W-90 flex fill that claimed to include a friction modifier.

Yes, it was easy to get into the differential by simply squeezing the bottle, but shortly after changing it I noticed chatter when I made a tight turn in either direction.

With 153K miles on the truck, I was thinking wheel bearings, universals and carrier bearing (that were changed not too long ago) or untested differential fluid.

So I decided to start from the back and go forward. I bought the standard, non-synthetic Valvoline 75W-90 and a separate bottle of friction modifier, dumped the synthetic and changed it out.

I did full wheel lock turns to the right and left and the chatter was a thing of the past.

 

I suspect there's another contributor to your issue and the difference in gear oil is possibly masking it. Ether way it appears you've eliminated the issue (or at least the noise) by going back to the original oil. I replaced both differential and transfer case oil with the same product (M1) 1000s of miles ago and there's no discernable difference in operation or noises (truck has 150K mi), Also consider that same gear oil is often used with good results by other owners on here.

 

The OP’s point was it was the same oil, just different packaging. I never trusted the “includes friction modifier” claim.