Ford F150 - rear dif making noise

ok guys i had rear dif rebuild. new axle bearings and seals ,now it is making noise when turning . i used 75x140 synagear gear oil. with a 4oz bottle of the aditive from ford . the truck is a 2001 f-150 4x4 with 355 gear ratio and 9.75 ring gear . it is also a locking rear dif.all symptoms sounds like chatter in the clutches but wouldnt the additive cure this?or is the 75x140 to thick a gear oil? thanks.

dang no help

It may seem odd, but our trucks call for the 75w-140 synthetic. That is the correct fluid. Have you tried cracking your fill port and dipping your finger in there for a fluid check???

I have the same problem. I'm wondering if the 4oz reccomended friction modifier is enough. I'm thinking of adding another 4 oz. Not sure what to do.

The clutch packs may be shot, I had to have them replaced on both my F-150s between 30 - 50K miles.

Give it a little time. I had the same trouble with mine, added the modifier, and it took about 400 miles for it to take full effect.