replaced lower ball joint-had car re-alined and new tires put on a month ago. now i am getting a thumping sound. as i speed up the revolutions get faster, and slows as i am slowing down. Could this be wheel bearing or driveshaft problem. It is a 4x4.

 

have you checked your u joints...front shaft and main shaft.

 

could be a wheel bearing, but hopefully its a U-joint. much cheaper and easier to fix.