I have noticed for awhile now that around 35-45 mph give or take. My truck will start bouncing in the rear. After 45 or so it stops and is as smooth as can be. I changed the shocks the other day but that did not help at all, any ideas.

 

These super duty buck like a wild horse sometimes. Depending on the road conditions. Its the trade off for have large load carrying leaf springs in the back.

 

Is the truck a CCLB??

 

Not sure what you mean by a CCLB.

 

Crew cab long bed. I think these configurations are more prone to the condition. I'm certain mine does it but it's not a huge issue I worry about.

 

It is, thank you for the help here and I think I will just leave it as well. Thank you

 

Shim the carrier bearing down.

Josh

 

Or maybe he has slop in the carrier bearing. If not, I would consider shimming it as well.

 

Correct, my first thought with driveline vibration would be u-joints and carrier bearing.

Next would be a lost driveshaft balance weight.

However, Ford has a couple TSB's concerning driveline vibration in the long wheelbase trucks and also the short wheelbase trucks.

For example my Supercab, Shortbed required taking the tapered rear blocks and swapping them side to side to cure the vibration at 50 mph.

The longbed guys usually just shim there carrier bearing down to cure there's.

 

How much do they typically shim it down?

 

https://www.ford-trucks.com/forums/1...with-pics.html

I've seen 1/2", 5/8" and even 3/4" spacers/ washers used.

Josh

 

Carrier Bearing is more then likely the problem at those speeds

This more for those searching bouncing and the above doesnt fit:
I have an early '04 350 4x CC LB its rough everywhere, like Heavy Assault said trade off for what the truck will do. There are two 10 mile sections of HWY where I live that when I am cruising @ 70mph I'm bouncing very harsh. I switch lanes and its good, or go up to 75mph and its tolerable. My dad told me every Ford truck he has owned (4 different yrs and models) did that in those areas, its just the "harmonics" (for lack of better word) of the bumps vs the wheel base. New shocks front and rear adjusted to max firmness helped a lot too.


Edited for readability

 

The long bed bounce is an inherant issue at certain speeds in the 03 thru 07's. Ford changed the rear leaf position and length in 08 to correct this. My 05 does it, only on certain stretches of highway, between 65 and 75 mph. When I have a load in it, it is not an issue. Just when empty. Put the wife in the bed instead of the cab. No more bounce and you can hear the stereo.

 

now thats funny

 

A friend's 2012 CCLB 6.7 has the bounce at 65...

Josh