where are the u joints located and how do i check to see if they are worn? thanks

 

u joints are on the front part of the drive shaft and the rear part also. it looks like a +. there are 3 ways to tell if it is bad, alot of vibration at speeds 30mph+, bad tin can sounding noise, and the last you need to crawl under the truck and like shake the drive shaft at the front and back by the u joints, if it is bad you can feel the drive shaft move like it is loose.