2000 f150 182000 makes a rumbling noise from rear end mainly when turning at slow speeds. Thought it might of been axle bearings so replaced them this weekend to no avail. I have the 9.75 limited slip rear end but what i found out this weekend is that the axle bearings are for 8.8 , the 9.75 bearings was to big. So does this mean I have 9.75 ring gear with 8.8 axles ? I have been using royal purple 75-140 with no friction modifier because royal purple says its it there. But after doing some research Im going to go get some friction modifier and see if it helps . So my question is how much of a pain is it to replace the clutch packs? what if i wanted to just put a different differential in and do away with limited slip ? Or go with a different aftermarket limited slip diff. ? what are my options , etc. Thank you in advance.

 

The clutch plates would lock up too hard from lack of friction reducing additive.
If you have no reaction driving relitively straight but an inside wheel spraggs in a sharp turn causing a rough feeling, it's the clutch paks.
You would need to put additive 'in' to reduce the clutch friction.
A way to test the clutches is to jack one wheel off, trans in neutral, front wheels blocked, and apply a torque to a lug nut.
Check to see how much force is needed to make the clutch Pak slip.
Do this for each side seperately.
If a torque wrench is used for testing, you should see about 40 to 60 lb/ft+/- before the Clutch pak slips.
If much more, some additive is needed. Much less, suspect the clutch paks of being worn.
Good luck.

 

thank you bluegrass I will give this test a try tomorrow. It does make the chatter / rumbling when I'm turning . Doesnt do it everytime but usually that is when it makes that sound. Looking at my local parts stores online and the only kind of additive they sell are k&w ,lubeguard , or champions brand. Can I get the xl-3 from ford dealership ?

 

At Ford, should be able to.
Any other brand, read the label to be sure what your buying is for the application.
.
This is one of those rare times when the rear fluid is not 'slippery' enough and needs 'friction modifier' to make it so. So much for Royal Purple!
Good luck..

 

Auto Zone sells a 7 oz bottle for $10.