Originally Posted by Decreasing Dave
I did Stewie. I added two bottles of the Auburn friction modifier. All was well until about a week ago.
Here's the thing. It doesn't do it all the time. It does it more when the oil is warmer. When it's cold, like just starting off, it doesn't do it. I have bought some friction modifier and I think I'm going to add a little more. Maybe the oil is failing, the original friction modifier is failing, maybe there wasn't enough in it to begin with and it's just now rearing it's ugly head?
The one thing I do know, is that if the Diff was failing, it would act up ALL the time. It's got to be oil/friction modifier related.
I'll post up how it goes in case someone searches out this thread someday.
**Haha - just looked at the OP date for this thread. Oops. I went straight to the end and saw the post today from
I wouldn't consider the Auburn worn out just yet. I had very similar issues with mine after changing the oil for the first time at around 12k miles. It didn't see any abuse, no hot rodding, no burnouts or trying to light them up around the corners - just highway driving and one hunting trip in some soggy mud and snow. No issues when cold, but clunky making bad noises intermittently when warm. When really warm, it would grab and chirp tires in tight, low speed corners like I had a locker. I was also using Valvoline.
Change the oil to Castrol Axle 80w90 Limited Slip Dino (NOT synthetic) and add more friction modifier. Add the FM first to make sure you get ALL of it in there, then drain what little is left in the FM bottles in to the gear oil and add the gear oil. I used three bottles of GM modifier (they are 4 oz instead of 6 oz like Auburn gear). Mine was VERY finicky about how much FM I had in there. I drained and refilled the oil several times trying different oils and FM amounts. It didn't like Ford FM or Valvoline fluid for some reason. Drove me nuts for a few weeks trying to figure it out.
I looked up the MSDS papers on the oils and compared them. Between Castrol and Valvoline, the kinematic viscosities are almost identical, but both the Viscosity Index and Brookfield Viscosity are higher on the Castrol. I'm not sure the Brookfield Viscosity has much to do with it (because it is measured at -26 degrees) but the different in VI might be enough to account for the difference in behavior. I spend many a hour on Bob is the Oil Guy and other forums trying to figure out what was going on.
But the Castrol 80w90 with ALL 12 oz of friction modifier worked best for me. That's been in there for about a year with 15k miles and the diff is still playing nicely and providing great winter and loose surface traction. It operates quietly, smoothly, and unobtrusively, even with the regular 30 degree daily temperature swings we get in the winter/spring - sometimes even from 0 to 50 degrees F in a few days.
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