98 379 grinding issues.

At what time do you here the grinding?

 

Please define grinding and bearings were out. Was it different from the first and second test drives? Replaced bearings in rear drive or front drive? Replaced the bearing by the yoke or pulled the unit out? Incorrect driveline phase or timing is a common cause of vibration and sometimes noise. If every shaft were out of the truck and all joints removed the holes for u-joints should align from end to end on each individual shaft. If a slip yoke is pulled off and reinstalled 1/4 turn off it is easily overlooked when assembled in the truck. A binding slip yoke can also cause some of these type problems. Jack rears up and idle in gear, iook for something bent.

 

Sounds like something in the front rear to me

 

My pete did the same thing around 55 to 60 and it was in the front rear but i cant remember exactly what it was.

 

That is the reason to look at it on an individual shaft basis. As an assembly from end to end it can look fine. Look at one shaft that is welded together at both ends. The shafts that have a slip yoke (free to move back and forth) and the one with a bolt on yoke for the carrier brg must line up the same way. End to end on each individual shaft must be the same. Then look for something bent, dents in the tube, or where welded balance weights have been knocked off tube. When something is worse after repairs than before it is usually related to the work done.