Hi all, I was searching for this particular problem but couldn't find the exact same thing. Please help.
I have a 2000 F150 4x4, it has 238,000 km. 4 wheel abs and 8.8" rear diff. Here is the problem.
The rear end of my truck has a growl this growl only occurs after the truck has been driving for a while so I am thinking after the rear end heats up. It happens dominantly when turning left and is gone when driving straight. I can really hear it on sharp left turns but again only after I have been driving it for a while. I am particular about my truck and maybe baby it a bit to much but I am a oil battery operator and my truck is an important piece of equipment. I do all my own work. I thought it was the wheel bearing but I want to be sure.
Thanks.

 

If it only does it while turning, I would assume you have a limit slip rear end and the friction modifier is worn out. Go to Auto Zone and get a 7 oz tube of modifier. Squirt it into the rear axle fill hole. Drive around and let it work into the clutch and see if that helps... Bearings will continue to make noise even when you drive straight.

 

If you have 100K miles on the rear gear lube, you might want to open the cover, clean and install new oil and the modifier.

 

If I change the fluids and add new modifier and it still does it will I be able to drain it into a clean bucket and fix whatever it is and use it over. I ask only because the 75-140 synthetic is $25/L and I need 3.5L. Also the Ford parts guy said if I am draining all the oil and cleaning it I should use 2 anti-slip additives. Does this sound right to you?

 

I've reused fresh gear oil. I drain into a pan and then pour back into a small container through a fine mesh screen in funnel or I've also used filter cones for auto paint.

I'd only use 1 anti-slip and just leave a little room in the diff for more if needed. Just bend a ty-rap and use it as a dipstick for the fluid check.