1999 peterbilt 379 ext hood bounce wobble

I have recently put a new front rear end in the truck bought 2 brand new steer tires had the truck aligned. I also just put a new transmission in the truck. I have no weird tire wear on the drives not steers now. I still have a terrible bounce. Also put new motor mounts in as well. Could I possibly have. Warped drive shaft?

 

Also I have checked my leveling valve and put it in every position possible. I also notice the colder it is outside the rougher the bounce is. I'm convinced it's a tire but when I jack the truck up and run it at different speeds there is no bounce or wobble from any of the tires all tires are wearing the same.

 

Thank ya!! I do feel it in the drivers set as well as the floor. I agree with you about it not being the front end. When you say steady bearing what exactly do you mean is that the same thing as the carrier bearing?
If it's the same thing I have replaced the carrier bearing.

 

When you say stub shaft is that the short shaft between the 2 rear ends? If so other than just looking at it I haven't taken it out and examined it any further. Yes it does change at different speeds. The u joints are not new but there is no slack and I have greased them. I didn't see anything wrong with them. Spline joints appear fine but a tiny bit of slack just very min. Slack. Drive shafts are in line I haven't had it balanced.
Wheel bearings are good they have been replaced a few weeks ago.
miles 1,847,000
back diff- I've replaced the bearings in the input shaft (front of back dif)
please do brainstorm I've been dealing with this for a while now. Any ideas are greatly appreciated.

 

It does do it bob tailing we've jacked it up put it on jacks a buddy of mine has rode beside me behind me we can't see a tire bouncing. But the warmer the tires get the less it does it but then sometimes it does it with speed as well. We've had warmer weather the past week and it was less intense now it's cooler again and it's bouncing hard. I'm debating a tire or back diff or warped drive shaft

 

Thinking back it began about 2 years ago I thought it was the trailer I was pulling at the time because it was junk and needed a lot of work but now I'm pulling a brand new Fontaine and I still have the problem at that time I put the bearings in the front of the back diff that is the only thing that's been done to the back diff I just recently put a whole new front rear end/ power divider in.. New transmission and all the other stuff I've done to it. I don't know how the drive shaft would be warped the trucks never had any damage. I did have some injectors in my truck that I had to take out because it kept gauding pistons. May have been to much torque and twisted or warped that drive shaft.