When I take off from a dead stop, more on a incline. I turn left or right I get a slight vibration. Sounds and feels like I’m driving on a highway passing line strip. Vibration feels like it’s come in the middle. Not sure. Ford F150 5.4 8 cyl. Rear wheel drive. 2010. Mechanic is saying rear differential.

 

If you have a limited slip rear differential. it's time for a fluid change. Use 75W140 full synthetic plus a bottle of Ford XL-3 friction modifier. Any brand fluid is okay and you can get the XL-3 at a Ford dealer as cheap as anywhere else.

 

Well i had the fluid changed,as recomended. No difference. I still have the vibration. Any other recommendations would be greatly appreciated.

 

Next step is to replace the rear differential.

 

Not so fast. It can take time for the friction modifier to work in to the clutches. Go to an empty parking lot and slowly drive it in a figure 8 pattern for a minute or so. The driveshaft should be inspected - u-joints and center support if it has one.

 

That's actually a good idea. Forgot about the driveshaft too.

 

Thank you for responding. It's been about a week and it's still vibrating. I brought it in for the rear-end repair. He said the rear-end was fine. It wasn't the problem. I rotated the tires. When i'm turning slow it looks likes the tire is hopping along the road. Like it wants to go straight. The tires have a little outer wear. Nothing major. It's still doing it after i rotated then tires. Not as bad though.

 

Does anybody have anymore recommendations? Nobody can seem to find where this vibration is coming from. Any help would be appreciated. It's almost 300 miles since the fluid was changed in the rear-end. Thank You.

 

Only other thing I can think of is the hub face is bent and not true. But that would also affect the rotors to some degree.

 

What fluid was used in the rear diff? And are you sure they used the friction modifier? Do you know if you have a traction lock rear? What is the code on the door sticker for the diff?

 

Thank for replying. I brought it back to the dealership i bought it from. I don't know what they used as far as the name. It is a slip differential. They did say they added the friction stuff. So i can only take there word. Can i add some or would that exceed the slip limit? At this point I' stumped. It looks like the tire is trying to slide straight instead of rolling with the turn.

 

I checked them when i checked to see if the calipers were loose. Everything looks fine. I guess checking the hub is next. I really didn't inspect that when i had the tire off.

 

You can add one more bottle of friction modifier.

 

When I changed the fluid in my 2000 F150 with the 9.75" traction lock rear using Motorcraft oil and modifier it still chattered on turns. I found out that on those models there was a TSB on the subject that recommended replacing the clutch pack and reducing the shim preload by 0.010". I just added a second bottle of the Ford friction modifier and the chattering stopped. So, I would do what glc recommended and add another bottle.