I have a 1999 Ford Ranger 2.5 4 cyl 4r44e tranny. The problem I am having is the rear bushing and driveshaft yoke went bad and broke the extension case. I went to the wrecking yard and found a replacement with new U-joints same problem. The bushing is wearing into the yoke on one side only. I hope I explained well enough for someone to help. Driveshaft does not seem to be out of balance or bent.

 

Are you describing a 'groove' worn into one side of the yoke where it is inserted into the tailhousing and wears against the bushing? If so, that would mean that the yoke was off-center from the centerline of the output shaft, and thus one 'spot' was pushed harder against the bushing. If the bushing was off center, all of the yoke surface would have been pushed too hard against the bushing as it rotated. The last alternative is that the output shaft is off center, and one spot is 'high', leading to excessive wear.
Last thought would be a misaligned drivetrain, but haven't given that enough thought to figure out if it would wear the yoke funny...
tom