2008 F250 PSD 4wd ext. cab auto

Trying to pinpoint this dang thing, truck has done with with 3 different tires. Acts somewhat like a tire balance issue but really don't think it is after 3 sets of tires and probably 10 rotations.

Anyway at just under 60mph it starts to shake, not through the steering wheel but more through the whole body/floor. Sometimes it is terribly bad other times almost not noticeable. If it is doing it and you take a corner it will go away more often than not but not always. It can also go miles and be very smooth and other times not. Had the front tires off to do new shocks, which may have helped for a week or so, and checked for play in the hubs/ball joints and nothing was noticeable. Steering is somewhat sloppy and truck has 105K miles, I'd say normal for the miles. A lot of the time you really feel it bad in the armrest, shakes it something awful along with the extended cab door area. Never does it under 60mph and either gets going so fast it smooths out some or goes away over 70mph. Pulling a trailer, goose neck, makes no difference, I did have a lot of weight( probably 500lbs at the tailgate) at the very back the other day and it didn't do it but may have just been one of the times it drove smooth.

Does it both with stock tires (265's) and some narrower ones (235's) that were on the last set. The steering wheel never shakes or tries to jump out of your hand like the death wobble, nor do bumps cause it.

 

It sounds like it isn't in the front suspension, otherwise you'd feel it more in the steering wheel.

That leaves rear suspension, rear wheels, or perhaps the drive shaft (or in the drive train anyway).

 

Been wondering that, I checked for play in the U joints and didn't see any. Still need to replace rear shocks.

 

Could you possibly have a wheel that is bent?

 

Sounds like the death wobble. Steering stabilizers help a lot!
Ford F-250 "Death Wobble" - YouTube

 

Also, you should check your carrier bearing and your driveshaft, incluing the slip joint. Also, examine the rear springs and the U-bolts for cracks.

 

Did you read the original post, where the OP says the issue is not felt in the steering wheel?

 

Forgot about carrier, had similar problem on a '93 recently and that is what it was.

 

I am just showing the video because if you watch the steering wheel does not shake. I just would like to make sure it's not that.