No, this is not about bad drugs. The 3.73 Limited Slip Diff. in my 2004 5.4L XLT 4x4 shudders and groans in low speed turns. Part of me says that this is normal for LSDs and this is how you know it's working. Then I heard that Ford issued a TSB in June 2004 on this issue. Anyone know what it said? Anybody else putting up with this "problem"?

 

Take it back to Ford and let them change out the clutch packs and ring & pinion along with grease.

 

I recently had a Ford LSD uit installed. After a few hundred miles, it started doing this.

After I had the fluid changed and added the friction modifier, it completely went away.

When was the last time you changed the fluid & added friction modifier?

 

I'll take it to the dealer. The truck has 8,600 miles on it and has done it since new. So the diff oil and factory additive are original.

 

I think the friction modifier is supposed to quiet the chatter. I bet they change out the fluid first. Since it's under warranty it's all good

 

It's a common problem. Ask or search in the 2004 F-150 section. There are tons of posts on this with mucho responses/information/resolutions.

 

Good news. The dealer just called and they are going to change out the clutch pack. Originally he said that Ford was working on another fix, but I guess that's still a ways off.