I'm pretty sure the max pressure on my tires is 35. I don't want to put more than that in them.

 

I don't know if this will help at all, but i just put in rancho 9000s on my truck, and it was riding the same way, rear end would jump/bounce over multiple little bumps or over large speed bumps. It felt like there was no control/stabilization(word?) coming down/off bumps...well in my n00bness i put the rear shocks upside down so i could adjust them easily...wrong, I flipped them and now it rides great. just my $.02, good luck in finding a fix.

 

I recently had a chevy s-10 that had the same problem. For me the answer was that the tires were out of round. If it has sat for any long period of time, or as tires wear they can slowly change shape. If you have an extra set, or can borrow another set try it. That was my problem on the s-10.

 

I sure seems like the shocks, but I put the factory replacement on it brand new a couple weeks ago.....

 

You would think if the tires were out of round that it would ride rough on the highway....but it is smooth as glass. I just had all 4 tires balanced and rotated, and they didn't tell me anything was wrong with the tires.

 

Today I was traveling downtown moving about 60 MPH and in a slight turn to the right when I hit a bump/expansion joint in the road....the back jumped like the tires came off the ground and it felt like I the rear end was going to come around on me for a second. It's got to be something in the rear suspension.

 

I may have found the problem....LOAD RANGE E TIRES!!. These tires are way too heavy for the F150 suspension. I'm going to try some different air pressures, but I think new tires are in my near future...it's a shame, cause these are still in good shape.

 

Yea, I would deffenatly try out some other tires, IIRC I have heard of a few people who do run load e tires without any problems. The E's have stiffer sidewalls and generally will make the rear less wobely.

 

A load range E tire is 10 ply, which is considerably heavier (weight) than a standard load range C. I am hoping that the extra weight on the suspension is keeping the shocks from being able to control them.

 

WOW, what a difference tires can make...I bought a set of Michelin 275/65/18 LTX A/S and they ride like a dream.....no more jiggly.

 

Good to hear!

 

Well I guess I jumped too soon. I am still experiencing some Jiggle. The other day, I was in the truck while my son loaded something into the bed. When he dropped the tailgate, I felt the same JIGGLE I had been feeling on the road thinking it was the tires. So I got out and lifted the tailgate about 2 inches and dropped it over and over, each time the whole bed of the truck would jiggle. Almost like the bed was loose. I checked and all the bed bolts are tight. So what could it be.....is the frame so weak under the bed that it can't keep things from jiggling around?

 

Ideas?

 

If you are running LR E tires at only 32psi, it is no wonder you are having problems. They should be around 50 on an F150. LR E does not make them too heavy and causing your problems. Many here run LR E with no problems, as have I in the past. At 32psi, it's a wonder you haven't had tire damage.

As to your new tires, those are a p series, make sure you run them at 35. Since they are not OE tires as were the ones you had on before, you cannot go by the door sticker.

 

OP Location? maybe someone near you could help you look over the vehicle