What causes the severe engine vibration at idle to low revs

I have a bad vibration starting around 60 and up in the right front. The tires were balanced, tires rotated, wheels changed, then tires replaced. Bearing were checked, everything is tight and within toloerance. Universal joints replaced, etc.
Cannot seem to figure out what the problem is

Yes all of that has been gone over and the mechanics can't find anything out of the odinary.

2004 ford ranger 4x4 4.0 6 cyl 89000 miles. Had rear brakes done 2 wks ago. First ride out at 50-60 mph it gets a vibration or shake you feel in the seat, feels like right rear out of balance have hade tires balanced rear drums were replaced in brake job were replaced again and balanced checked all good. It still vibrate/shakes at 50-60 mph, almost constant. It fades from time to time. Any suggestions?

Yes they did, and have since replaced the new ones, and it still happens. Took it to another shop and they test drove it came back looked ath the shocks ujoints supsention, then checked th new drums and noted that this 2nd set were warped and needed to be replaced.

Hi, I have a 2001 ford ranger 2wd 3.0 automatic. At 60mph the truck vibrates pretty bad. I put new tires on it checked the front end seems tight. Any ideas would be great. Its fine at slower speeds and seems to be fine at about 70mph but not at 60-65.
Thanks dave