Vibration starting at 40mph

[Snowmanii]

94 crew C3500 automatic flatbed.
I can feel vib starting at 40 and gets worse to 65. Afraid to go faster than this as one time i did, ujoint popped out. No noticeable up and down or left and right shake in steering wheel.
Replaced:
1.R/h axle seal and brake pads (dont think this had much to do with issue, but first thing i did when i bought truck due to oil coming out from drum)
2. Ujoints
3. Center driveshaft bearing
4. 4 new tires installed and balanced on rear.
Front tires good, balanced.
Driveshafts balanced together.
Ideas?

 

[michael hurd]

Check the transmission mount.

I would lean towards an issue with the driveshafts.

 

[Dr.Zoom]

Is this since the new tires or was it going on before?

 

[Snowmanii]

Is this since the new tires or was it going on before?

Both before and after rears new and front balanced.
I'm starting to think its in the front end or possibly trans/engine mount. Next I'm going to jack front up and shake everything down.

 

[mattbrat004]

I'd check from the trans mount back. I don't think itd be the front end especially if it's still driving straight.

 

[Bob L]

I would jack up the rear put it on good stands and run it up to speed and see if it vibrates still. Sounds like a drivetrain issue to me also.

 

[chevytrukk24]

mud, snow, ice inside the wheels? lol