I have a 2005 F150 Lariat two wheel drive. Has 111000 miles and in last 500 miles I have noticed a slight slipping of the trans or rear end when I start off. This feels like the wheels are spinning in gravel for very short time. Like until it grabs. I mostly notice it when i come to a complete stop and then take off. Harder I take off worse it is. Turning even worse. If I barely gas it it almost doesn’t do anything. Never does it any other time. I can also feel it. This only lasts about 1 second or so. One mechanic greased it with some special grease. but said I need a new rear end. Grease worked about a couple weeks then right back to this. I question that I need a new rear end but no clue. Help!!

 

If your truck has a traction lock rear, the clutches could be worn out. Look at the sticker on the door jam and tell us what the rear end code is. If the clutches are worn out, they can be replaced. Not such a big deal.

 

 

Yes, that's limited slip.

Change the differential lube. You need 75W140 full synthetic gear oil (any brand), and a bottle of Motorcraft XL3 friction modifier.

 

Yea. That was all done. Worked for a week or so then same.

 

Add another bottle of friction modifier. Some of the Ford 9.75" rears need 2 bottles to smooth it out.

 

If the clutches are slipping, friction modifier will make it worse. If they are "chattering" on a turn, it could be the clutches don't want to release and more friction modifier should help. Sounds to me like the cluthes are slipping too much and a new clutch pack is needed. It can be replaced without disturbing the gears, so a shop that knows how to do it should be able to change out the clutch pack pdq.

 

I feel like clutch pack too. I had one mechanic say I need a new rear end. Seems odd to me. Definitely like the idea of clutch pack.

 

Here is a link to a Chris Fix video showing the installation of a new clutch pack in his Mustang's 8.8" differential. This should give you an idea of what is involved.

 

If the clutches are wore out, you just loose the trac lock or "posi" aspect, it then just acts like a regular open rear end.