My '74 sounds like someone is under the car tapping on the drive shaft with 12mm wrench. Totally random, all speeds, accell, decell, cruise, tap, tap, tap at the whim of some gremlin. The carrier bearing was sagging so I repaced it. The joints felt fine, so I reinstalled the shaft, but no change in the noise. Guess I'll have to replace the whole drive shaft. Has anyone seen a driveshaft that appeared good off the car but not on? Que paso???