My 2004 FX4 Screw makes a major vibration from standstill to turning in both directions. Only does it if at a stop then turning, not straight on. Its getting much worse over the last several days. The vibration is very noticeably coming from the rear, not up front under my feet like the tranny probably would. What are your thoughts?

 

Limited slip clutch chatter. Change your rear diff lube, use 75W-140 full synthetic and a bottle of Ford friction modifier.

That assumes you have a limited slip rear.

 

Also might take about a hundred miles to work in and feel a difference.

 

Thanks guys! Will change the fluid when I get back in town, as always the info is much appreciated!

 

x 2 !

 

Mine started to do that Saturday night along with a clunking coming from the rear axle. Turns out some how I broke the LS cross pin and the pin bolt into 3 pieces.

 

I just put the Motorcaft Friction Modifier in mine about an hour ago and it seems to have fixed it. Mine started earlier today and was pretty bad a few times, I thought I was going to lose my rear end in no time. Put the modifier in and did about 10 figure 8's and went for a test drive and seems better than ever.

Just make sure you have a flexible funnel when you put it in. It's kind of a PITA.

 

I put new fluid in about two weeks ago and have put over a 100 miles on her and, it is much better but I still get enough vibration from stop and go turning to slightly vibrate the mirror like I was pumping some bass. Everything looked good and solid when I pulled off the cover, no shavings, metal pieces or anything like I thought I might find. Just really old fluid, not even burnt just old. So any other ideas?

 

What exact fluid and modifier did you put in?

 

75W-140 synthetic, I went with Royal Purple mainly because a buddy of mine runs it and keeps yappin about the stuff. I didn't get the Ford friction stuff (and this maybe is where I messed up) the bottles say they already have the friction reducer in them, so I did not buy the reducer. That might be what I should do. I am just ready to say what the heck and dump some in, I don't imagine it could hurt.

 

Go buy a bottle of the FORD modifier and put it in.

 

Ford friction modifier is now in. I will report back after a few days. Thanks for the input glc.

 

I took mine in last week for a similar problem. The service department said it was clutch packs in the rear diff. It will be about 30 days for parts.

 

Ssame - Post back when/if they fix it and what they really found once in there. Mine is still doing it, not as bad since the Ford friction modifier was put in. I might dig in and replace the clutch packs this weekend if time permits. Will post up my find if I get to it.

 

Will do. I have not got the phone call yet, as soon as it's done i'll let you know.