I purchased a used 2008 F150 with 62,000 miles. The truck is in excellent condition and is a crew cab with the short bed and the 4.6 v8 engine. I changed the 17 inch wheels to a set of Ford 18 inch wheels with Goodyear tires that came off another 2008 F150( XLT model). The tires had less than 15,000 miles on them. Since that time I have replaced 3 of the 4 tires because I could not get the tires to balance out properly. I have had all the tires and wheels balanced with the road pressure balance and the front and rear end have both been aligned. I CANNOT get the RIGHT REAR of the truck to keep from bouncing and hopping at almost any speed. It changes from day to day a little bit but while slowing down I get the hop vibration( when I apply my brakes) and while at speed ( mostly 45-55) and above 65 I can constantly feel the truck vibrating. It is apparent it is the right rear. I took it back to the dealership where I bought it used , they could not find any issue. At some time, the rear cover to the rear end has been taken off but I cannot find any information through normal channels as to why. I was told by a Goodyear dealer it is a KNOWN problem with this truck but no one else advises that. I was by the shop that balanced the tires it is a Goodyear problem. All I know is that I cannot enjoy my ride due to this very apparent hop/bounce from the rear end. The alignment shop said they could not do anything more to make it better. Is there a FIX to this? Is it a problem with this model truck? Any suggestions greatly appreciated. The truck has 69,000 miles on it now.

 

The tire dealer is feeding you a line about the "known problem".

Take each of the tires off and roll them slowly on on a smooth paved surface and see if you can detect any runout or out of round in them. You may have a broken belt.

Check your brake rotors for runout. Also check your parking brakes; I've heard mention that they sometimes stick. I would even raise the rear of the truck and spin the wheels looking for any rotational anomalies.

How are your rear shocks/springs?

 

As far as I know, everything under the rear end in regards to the suspension is good and correct but I am going to get it checked out again to be sure. Of the set of four used tires that came with the wheels, two were so bad, the front end/alignment shop could do nothing to get them to balance within standards. The Goodyear dealer actually replaced one tire free and on the other two, I basically got two for the price of one. When the alignment shop was trying to balance the tires they checked out the brakes and everything was okay. For about three weeks after I replaced the third tire and had the front and rear alignment done, the ride was decent but I still had the vibration on the pedal when I applied the brakes and when the tires were cold. I am even running much less air than recommended to give a softer ride even though I know this speeds up tire wear. Now however, it does not matter hot or cold, I have a washboard type ride from the right rear. There are some speeds that everything runs smooth but for the most part, the bounce is there.
I plan to go back to the alignment/balance shop for another look based on your response. Perhaps the 4th tire now has a problem as well...Other than this, this F150 is the best vehicle I have owned but the bounce/hop ride is taking all the fun away from driving. Appreciate your response. I will update.

 

Spent 3 plus hours at mechanics garage/alignment shop. Checked drive shaft, checked brake rotors, checked wheel/tire balance, checked alignment, checked rear end and then pulled the shocks. The truck has 69,000 miles and this should not be an issue but each shock had a weak spot in regards to the "rebound" or recovery. Replaced shocks and I would say 80 to 90 percent of problem went away. I believe what I am feeling now is what to expect in a short bed crew cab truck. Problem appears to have been resolved.