8.8 TracLoc chatter after warming up

[skidd]

I've lots of experience with various chevy LSDs and and import ViscusLSDs and what not.. this is my first ford 8.8 TracLoc.
The clutch packs chatter pretty loud on corners... after the diff fluid is warmed up. Not when it's cold.
Sometimes it's just a loud whine, some times it sounds like metal biting metal as I feel the packs jump, rather than slip.
It's a rebuilt diff with new steels and fibers. Full of Mobile 1 full synth 75w-140 and a bottle of Ford Friction Modifier.
When the diff is cold, or just staring out. it's quiet. After a bunch of miles when I assume the oil is warming up, she gets louder and louder.
I spent about 10 minutes last week doing slow figure 8s in a parking lot. Didn't change anything.
Is this typical of the 8.8 TracLoc? Should I just keep driving for ??? miles to see if it goes away?
Do I bite the bullet and re-do the clutch packs? Is the fact that it doesn't start until the oil warms up something to look at?
Advice?

[johnnybgoode]

Are you sure it not rear brake moan? I thought mine was the dif too but then figured out it was the brakes. Just a thought. Scott

[Gordon Levy]

Go to a parking lot and drive in circles, first left and then right. You may need to do 10 minutes in each direction and you do not need to go fast.

[NAZ]

I believe if you're running Mobil 1 synthetic you don't need the friction modifier.

[Gordon Levy]

You still need to run friction modifier. There isn't enough added to off the shelf oils.

[Frank Messina]

If the person that rebuilt the differential substituted an S spring out of a Ranger instead of the original factory spring in a misguided attempt to improve internal grip, that setup will definitely chatter in the corners.

Frank

[skidd]

guess I'll go do 20 minutes of circles in a parking lot. See if that does anything. Hopefully I can resist the urge to turn the "circles" into "doughnuts". ;)

[CraigS]

Question; does the chatter sound like it's internal to the diff or is it the tires slipping slightly. If it's the tires slipping slightly, I would let it go. Mine does that because I used Mobil1 w/o an additive which definitely makes for a tighter lim slip action. All the additive does is allow it to slip more easily.

[skidd]

It's an internal sound. Even changes slightly depending on which direction I'm turning.

[rich grsc]

Not sure that will make a change, but the correct fluid would be 75w90, 75w140 is usually used in trucks.

[scottiec]

The 75w 150 vs 75w 90 has been flip flopped a lot with ford. I believe it is all spec'd for 75w140 now. Either way, It depends on what type of duty the diff will see. (In the time I typed this, they probably changed it again lol)

Also, if circles make you dizzy, tight figure 8's work too.

[skidd]

10 minutes one way, 10 minutes the other way. Substantial improvement. Still a little bit noisy, but a heck of a lot better. Planning to drive it into work tomorrow, so I'll see then if that did the trick.
Thanks guys.

[CraigS]

I think you are on the right track. It may just need a little more time and a longer drive won't hurt. I have seen suggestions that while rebuilding the clutch pack it's a good idea to soak the discs over night in the modifier. So I can imagine that once it is assembled w/o doing that, w/ the S spring pushing the discs together, it may take a while for the fluid to work it's way to where it needs to go, in between each of the discs. Getting it warm and the oil thinned out on a longer drive has to help.

[skidd]

Drove more than enough today ...no more noises... Other than the odd buzz... Nothing like before. Thanks guys.