2009 Ford F150 Shudder

[fishhuntwork]

I have a 2009 f150 crew cab with a 5.4l, 49,500 miles. It has a shudder or vibration when either starting from a stop or making a slow turn, worse when towing the boat. I did install a level kit in approx 1 year ago but this started after that. I also tried changing the rear axle lube and I did install some friction modifier. Could this be related to the blocks I put in the rear or a pinion angle problem?

[i'majigger]

I had a 2006 F150 that did the same thing. It is the slip clutches in the rear end that make the shudder. I talked to the mechanic at my Ford dealer and he said just go ahead and drive it. They are not wore out or damaged the just slip a little when making a turn or starting from a dead stop. Looks like your pick-up does not have a lot of miles like mine did, so it does make the shudder worse from the truck sitting alot.

[JOHNBIGDOG]

I would second the possibility of the clutches in your limited slip differential, If you do indeed have a L.S.D. (Not the drug.) It may help to throw in some more friction modifier, but I have found that it doesn't, the clutches are shot, and need replacement.

[tonkapat]

put in 2 bottles of the modifier from ford per rear diff change. Will take a little while for it to soak into the plates.