Crow27

I am having an issue very similar to this. It'd driving me insane..

snobdds

It's called axle wrap. All the F150 suffer from it in one way or another. The problem is the soft springs that give the truck a nice ride, but sacrifices in the stiffness to prevent axle wrap.

There are a couple of solutions.

The RASS system for the leaf springs.
A track bar in back.

The new 2015 F150 have a shorter rear leaft springs. I don't know yet if that help in any way...

mgarton

I've read the axle wrap threads, but wouldn't axle wrap happen regardless of front wheel orientation? It's only doing it when the wheels are turned which doesn't make a bit of sense to me

Side note, I got my buddy's GoPro this morning. I'll post a video from underneath after I figure out how to use the darn thing...

mgarton

SUCCESS!! No more shaking!

Here's how I figured it out...

I got some video from underneath and found no shaking at the transmission and no axle wrap. I then decided it had to be the differential. I took the cover off again and drained the fluid. It was kinda dark brown which was odd since I had just changed it, so I decided to put new fluid in. I used cheap stuff from the parts store last time, and figured maybe I should try the more expensive crap from the stealership.

I get to talking to the parts guy about my problem and he says he knows exactly what it is. He says you've gotta put friction modifier in it, but I told him I didn't think I have the limited slip diff. He takes my VIN and looks it up in the computer. Lo and behold, my truck came with an LSD. I've always seen LSDs with clutches or whatever in place of the spider gears, and apparently the clutches in the ford diff are NOT associated with the spider gears. My mistake!!

So I get the oil and modifier, put it in the diff, and it doesn't shake at all now! Moral of the story, know what equipment your truck has and use the right stuff!!

Thanks for all the replies and I hope this helps someone else

Whalersailor18

I have the exact same symptoms you have/had and I hope your fix sticks, I did the same using Motor-craft oil and the additive and it worked fine for about a week and then the vibration returned. I have same year and model as you and this has been driving me crazy with little to no help from my Ford dealer. I am now at a point where I am considering replacing the rear springs with a stiffer set, new bushings and possibly a set of shims to align/reduce the axle to rear yolk offset (anyone out there know the part number for the spring upgrade?). I have also noticed that my right rear wheel wants to break traction upon moderate acceleration. It tends to vibrate more noticibly when it is warmer out. In the dead of Winter it was much less frequent until I had been driving a while and things had warmed up and worked themselves free. While on a lift the other day I noticed the leafs moved/shifted when I spun the left rear wheel. I also noted that the thickest portion of the spring was sitting cocked in relation to the other two on the left side. Since this did not begin to happen until I hit about 55K miles (now have about 75K), I am thinking that the springs, bushings and other suspension parts have worn/broken down and are allowing more movement in the rearend upon acceleration. I hate to throw money at the problem in the hopes that it will resolve it, but without Ford stepping up it is hit or miss and this is just the next logical step in finding a solution.

tomasulo

Same issue here on my 2011 Ecoboost. Notice a shudder/binding from a stop, only for a few seconds, then not noticable again. From a cold start this morning, I noticed the feeling when in reverse, backing out of parking lot, again only for a few seconds. Nothing noticable at normal driving speeds. I did notice a bit while slow and turning too. Same thing as the other forum members do you think?

tomasulo

My dealer seems to think the truck may need a clutch pack. It's most noticeable after sitting and when first startup and driving away, but also noticed from time to time during the day, when it's already warmed up. Anyone have the clutch pack changed out?

justjimmy

When I bought my 2011, I had the same shake. Dealer changed the clutch pack at around 1000 miles. It did nothing.

I added RAS and it solved the problem.

My 2 cents.

Whalersailor18

Jimmy, what is RAS and how many beans did the clutch pack set you back? Just curious.

UPDATE: I drained and replaced the rear gear box oil and added new fluids including friction additive. The shudder immediately went away and I have not had it return. I have easily put 10K on it since with no issues.

tomasulo

Yeah. What is RAS?