What do U Joints do? Mine on by 83 RX7 are squeeking, and I'm told they need to be replaced.

 

U-joints allow the ends of the driveshaft to move laterally. This is so the rear end can move up and down, the transmission can bounce a little and any misalignment in the driveline is compensated for.

Most communities have a driveline shop that can replace the u-joints for a reasonable cost.

 

time out aaron. dont you have to replace the whole drive shaft as the u joints are not replaceable?

 

If you go to a drive train specialty shop, they can replace them. But, yes "officially" from Mazda they are not replaceable. A typical auto repair shop won't be able to do it, but a specialty shop will.

 

What he said. A driveline shop can also build you a shaft using any U joints you want. My shaft was built to take Dodge truck joints which are strong and inexpensive.