vibration

[mike.strout]

i just bought my 1999 f-250 SD 7.3L powerstroke like a month ago. im getting a vibration when driving in 3rd gear at about 16 or 1700 rpms (starting at about 40mph) and it goes untill about 50 when the rpm's get around 2000 or above. this also happens in OD when the rpm is the same and speed is from about 45-55mph. only happens on accelaeration, and if im in the pedal good, it doesn't do it at all. cruises nice, this only happens on acceleration and in 3rd and OD when rpm is at 1700 or so and speed is 40-55mph. everything else=fine. any thoughts?

[greasltn]

Simple things first, check the u-joints.

[melmount]

mine had this exactly.
I replaced u joints, had the shaft balanced, I still need to replace the slip yoke.(little loose) I replaced the tranny mount too.

[mike.strout]

thanks guys. i really just want to hear that its not the transmission. which i doubt it is cause it shifts mint through all gears. just the vibration is happening.