Hey guys,
So I bought a truck in December I really like the truck it fits the family and my needs as a truck and I am not wanting to replace the truck.

I have an 2005 5.4 FX4 4X4 the only thing that was added to the truck is a 2" leveling kit. With I think 3.73 rear ended and 168k miles

My issue is with the rear end. This does not happen all the time. When I leave my subdivision I always turn right then left on to the Main Street. When i turn I can feel the rear end "binding up" or vibrating like it is locking up. I don't here any noise and I don't remember this ever happening when I turn right.

I have check the U joints on the drive shaft and they are good. I don't now anything about a rear end on then then what they do and what a limited slip does.

Any advice is help full

 

If it has the limited slip rear end it is most likely the clutch packs. They may not be bad. You should have the rear end grease changed first. Make sure they use the proper grease I think 75w-140 is right. Make sure they use a friction modifier IF you have the limited slip rear end. It is a common problem for Ford LS rear ends. My wifes Explorer had this problem. I just removed 4oz of the diff grease and added 4oz of friction modifier and the problem went away. A dealer might try to sell you new clutch packs for about $800 I recommend just making sure you have the proper grease with a modifier in it first and waiting a few months for the modifier to do its magic. If not after that you may be at the point you need new clutch packs.
https://www.f150forum.com/f4/how-cha...08-f150-83334/ not my write up but it gives you a good idea of what it takes. Make sure to add the friction modifier first so you don't run out of room for it.

 

Sounds like a clutch pack issue in the rear differential. You could try servicing it. 3qts of 75W-140 differential lube and 4oz of Ford Friction Modifier. The previous owner could have serviced it an not put in the required friction modifier. Smarter people will weigh in, but that's where I'd start.
EDIT: While some differential oils may come with friction modifier in it, I've always added the Motorcraft FM.

 

Thanks guys three more questions.

1) is this all stuff that I can get at NAPA/ Autozone...?

2) As I will be doing this work how do I know if I have a LS? or what is the best way to find out?

3) just to make sure I under stand this is not going to be an quick fix, in the fact that the oil will need time to work?

 

I used this and added nothing, says "Limited Slip" on the bottle.

 

Yes, you can get it all at a local parts store.

To find out what axle you have, look at your door sticker and google the 2 digit axle code. It will give you the gear ratio and whether it's LSD or open-diff. Alternatively, you can look at the tag bolted to your diff cover.

Despite the above post, most of the group says to add the friction modifier EVEN IF you buy the gear oil with it already in it. What you do is your decision.

It'll take some time to work the fluid in the clutches, just find you a big open area and do some figure 8's to get the fluid and clutches moving.

 

^^^ Yes what he said.


IF you have a LS axel you will want to add a friction modifier even if the rear end grease says it has it. IMO you should get the motorcraft friction modifier from a Ford garage rather than an off brand. Its only $8 a bottle where I live. The rest you can get from your local NAPA.

 

Try Fiber One tablets for a binding rearend.
Great advice given so far. Do as others have said, try servicing first.

 

Just an FYI

While the rear end fluid is thick, it is an oil, not a grease.

 

Eh tomato, tomato LOL I am aware just always called it grease, don't know why.