Eaton aftermarket posis and Ford factory limited slips are 2 different animals. Ford *requires* synthetic 75W140 and modifier.

 

I'm going to try the trial and error thing here and lets yas know .. I have to change dif oil anyways and with any luck that will fix my shutter .. but if not .. any idea the cost of the clutch packs and if it's a do it your selfer job ?

 

My truck was doing the exact same thing. The shuttering when turning from a dead stop either left or right, it didn't matter. I took it in to get the diff fluid changed and it went away for about a week...........and now it's back. Any suggestions on what I do? Do you think they never put the addative in! I don't know. I'm very frustrated with it all.......please help!:bows

 

Only one way to find out - ASK them.......and ask them what exact fluid they used too.

 

I am encountering the same issue with my 04. What does Ford suggest to do to fix this problem?

Carl

 

I had this problem on my '03 with less than 70,000km. I have the H9 rear end, which is the 3.55LS. The dealership told me my clutch packs were worn out (without even opening up the diff to check, figure that one out) and that it would cost $600+ to fix, and that it wasn't under warranty. I told them to just change my diff oil (like I asked in the first place), and make sure they added the friction modifier. Guess what. Problem fixed. Smooth as a hot knife through butter.

 

I had a slight shutter as well in my 04. Just changed the fluid out (54k on the original) and put in Royal Purple 75w-140. RP has the friction modifier already in it so nothing else added. Got it for $10.99 a quart from Consumer Auto Parts.

So far the shutter is gone and it is noticeably smoother on slow turns. I'm taking a 200 mile drive this weekend so I should know after that if this $33 fluid swap fixed the problem.

 

Good call on your part. BS on the dealer's part. Worn-out limited-slip clutches will, if anything, make it smoother and quieter, not rougher or noisier. When the clutch packs wear out, the clutches lose their grabbiness, and it essentially becomes an open diff, and will be as smooth and quiet as an open diff.

In other words, the only consequence of worn-out LS clutches is that you lose your limited-slip effect. You can still drive like that forever.

If the clutches are nearly worn-out, changing the fluid and leaving the friction modifier out is a poor man's way of buying a little more time before clutch pack replacement. Leaving the modifier out would restore a little grabbiness to the clutches until they are gone completely.

"grabbiness"...did I make that word up?

 

Good thing for the extended warrenty. I just had my truck in: spacer, rear-axel oil, friction modifier, cluch pack, brake shoe and lining, brake drum spring, and all four ball joints. Also front sway bar link was loose. Total charge to me: $100!

I would suggest to take your truck in to have the vibration looked at.