Howdy yall. So I've got an 08 Lariat crew cab 4wd. Just broke 100k and I've noticed the rear end shudders when I accelerate from a stop but only when I'm turning left or right. Just had the diff fluid changed b/c the dealership I bought it from (Chevy) had regular diff fluid and I've been told it needs limited slip fluid. Any ideas ?

Merry Christmas

 

Just what did the Chevy dealer put in it?

 

It needs 75W140 synthetic gear lube and a 4 oz bottle of Motorcraft XL-3 friction modifier additive if it has a limited slip rear. Take it to a Ford dealer or buy the right stuff if you do it yourself.

 

glc is correct. It needs both of them. Hopefully the clutch packs aren't too destroyed.

 

I fixed my shudder just by adding a small bottle of the friction modifier additive from the dealer. It also stopped throwing a code for the rear speed sensor when I did this. Be warned: the friction modifier is some very nasty smelling stuff. One drop on my garage floor stunk up the whole house!

 

Yes, but we don't know if the proper fluid was used.

 

Easier to quote the correct response than to write it again .....

 

I had the Exact same thing happen at the same mileage. What GLC told you will fix your problem! Ford likes to tell you that you never have to service this but that's BS. They will also tell you if you have this shutter that your clutch packs have to be replaced. Also BS. I have 40,000 on the new fluid and still no shutter.

 

Thanks for the input guys. I've give it a shot

 

I used Valvoline 75w140 synthetic in mine and it came with the friction modifier so I didn't have to add it separately.

 

Sooo, the friction modifier did not fix the problem. Gonna drop it off in the shop. I hear the clutch pack might be messed up.

 

Did you change the fluid with the proper lube or just add a bottle of FM?

 

It also takes a bit of time to work the FM in to the clutch packs - you can help it along by driving in a figure 8 pattern for a few minutes.

 

Mine has been doing this for 2 years. Replaced the fluid with updated viscosity and added a bottle of FM as instructed. It did not fix it completely, but it has not gotten any worse, either. Until the rear end falls out I have learned to live with it.

 

Some of the older trucks, such as the 2000 I used to have needed two bottles of FM.

There is a TSB for those older models that said the fix was to replace the clutch pack and shim it 0.010" less preload. i just put an extra bottle of FM in mine and that fixed it. I know it worked fine for 90k more miles before I lost track of the truck.