squirving88

I have a 2005 F150 lariat 4x4. When accelerating and turning to the left the truck starts to vibrate and shake. If i turn slowly it doesnt do it. I read a little and read something about the rear end clutch packs? Could that be it? I also read something about friction modifier. I also dont know if my truck has a LS or not. Can anyone point me in the right direction?

Mod (Ret.)

Post the rear end code here and we can 'cifer it. The code can be found on the drivers door jamb (large decal) or on a tag mounted on one of the rear end cover bolts.

And if it's LS, it most likely needs a rear end fluid change with modifiers added....how many miles are on the truck? Has the rear been changed before?

otto457

Start by looking at your door jamb sticker and determining if you have LS or not. If you have LS, a bottle of Motorcraft friction modifier and your favorite 75w-140.

19-3.55 non-limited slip (Econoline, F-150)
18-3.08 non-limited slip (F-150)
17-3.31 non-limited slip (Econoline, F-150)
H9-3.55 limited slip (F-150, F-250)
B6-3.73 limited slip (F-150, F-250)

squirving88

it says B6. The truck has 113k miles on it. I bought it about two months ago. It looks like they replaced the differential gasket on it

Turkey Hunter

Theb you need to drain the fluid and refill it with synthetic 75w 140 and add 2 bottles of friction modifier. Should solve the problem.

squirving88

Thanks for all the help guys

k.chaloux

I had that problem, dealer replaced the ring and pinion 3 times, and then finally the clutch packs and it went away

phenrichs

Wow, hope that was under warranty. I would have started with the oil and friction modifier.

Blown Ford

The symptoms described above by the op point to the limited slip failing. Replacing the fluid and friction modifier would be a waste of time. The clutches in the LS are shot and hence the reason you feel the shudder or chatter when turning or accelerating quickly. The shudder feeling is the clutches grabbing and slipping repeatdly. Need a new LS or my preference would be a True Trac. Contact Wayne at www.diffsonly.com via email and he will give you a great deal.

kevhead75

Generally when the rear end is shuddering around corners the LS clutches are grabbing. As stated above changing the differential fluid and adding 1 bottle of friction modifier is the cheapest and easiest route to go first. If it still does it after that you can add one more bottle of modifier. If continues after that then Blown may have a good contact for you. Typically most top shelf synthetic gear oils have some friction modifier in them already. Not to start a pissing match about oils I would recommend Amsoil severe gear when it comes to gear lubes and one bottle of Ford friction modifier. After you change the fluid find a open parking lot and do some slow figure 8's to work the new fluid into the clutches.

Kev