What are the symptoms of a bad U-joint? I can cruise real slow in 2nd gear and hear it pop. It's a random pop, but sounds the same every time. Just noticed it today.

 

u joint squeel or clunk most of the time. if it squeals, it will usualy be at a certain speed range (a lot of times low speed). if it clunks it can be at random times and speed. to physically check, get under the car and shake the driveshaft. do some light prying. you shoud not feel any play.