In any gear accelerating between that speed the front of the truck jerks up and down violently. Only time it doesn't do it when I push in the clutch or stop accelerating.
If need be I will make a YouTube vid
sincitylocal
+1y
Check your u-joints, and carrier bearing if you have a 2 piece shaft.
befarrer
+1y
Second that motion.
U-joints are staked in on these models, they are replaceable, but are more time consuming and annoying lol. I have to tackle that job sometime soon.
mazdatweaker_2
+1y
Check for a tread separation or maybe one of your tires coming apart. You might have hit a curb and broken the tire internally.
added edit;
you could have picked up a nail which allowed water into the tire, which would have allowed a steel belt (if any) to rust, causing tread to bubble. That one happened to me.