My 01 super crew 2x2 has a strange grinding noise at the REAR WHEELS when I turn the wheel at low speeds, forwards or backwards. My diff and transmission oil have been serviced recently so I'm thinking/hoping it's as simple as an emergency brake shoe hanging up or something related to the brakes. I've got 150k miles and other than this, it's as new as the day I bought it. Anyone have any ideas?

 

I would add a tube of friction modifier to it.

 

A tube of what? To where?

 

Ok, I've searched information on Friction Modifiers. There are so many brands and price points, I could use some help. Redine, Royal Purple, Motorcraft...the options are endless and so are the prices. Anyone with some more suggestions would be appreciated.

 

You only add friction modifier if you have limited slip. You might have a bad wheel bearing.

 

check your axle code to see if you have a limited slip. if not i would check the wheel bearings first

 

Before you start throwing money and additives at it I would pull the rear rotors and check out the parking brake shoes . These are well known for the lining falling off causing the same kind of grinding noise you are talking about

 

Jack the rear up, and spin each side.
Find out if the grinding is coming from only one side, and vibrating the noise to the other side. Or if it's something they share such as your differential. Might be hard to replicate the noise if it only happens while turning though. There's no single reason why it might be that way, could be worn shock(s), cupped tires, feathered tires, out of alignment, maybe even different tire sizes if one's worn more than the other. Check to see if the bearings have unnecessary play by shaking it. Also check to see that the brake caliper(s) aren't sticking and in need of a rebuild.

Can you isolate the noise to a specific side when you drive?

 

if it only happens when you turn and at low speed, and you just had the rear oil changed, then the oil is a good bet. the friction modifier changes the oil quality and makes the limited slip clutch "give" a little when you turn at low speeds. otherwise you get a jerky motion. you can get a 7 oz tube at Auto Zone that meets the FORD spec. add the whole tube, dont believe 4 oz is enough. It cost less than $10.

 

I have an '06 supercrew and over the last few month have noticed the same thing progressively get worse. I took it to a reputable auto shop and they seemed to think it was coming from the clutch packs. They opened it up said there was some "tarnish" on the plates, cleaned it off, added new oil and limited slip fluid, and it still does it after it warms up.
My next move will be to jack it up and check the play in the wheel bearings and the rear brake packs per some of the other posts. Any other ideas out there?

 

it could be your clutch plates in the rear end. they are grinding when turning corner. actually gm lube works best in the rear end

 

woody, how much addative did they install? did it get better after the drained and refilled and added the friction modifier? FORD says to add 4 oz, you really need about 7. If its better, but still there when warm, i would add a fill bottle. get it at Auto Zone.

 

Its still there. I don't know how much they put in but will ask them, Auto Zone is on my list of things to do today for sure.