I bought this 77 CJ5 a couple weeks ago and drove it to the beach yesterday for a spin. When in 4WD (either mode) there is a loud banging/rattling that sounds like it is coming from the front drive shaft. In 2 hi there in no sound. If the front hubs are locked and the T case is in 2H it still makes the noise. If the T case is in 4WD without the front locked it still makes the noise. It is not constant and seems to really increase under load. If you are slowly driving it doesn't make any noise. If you accelerate it quickly bangs and clunks. The front wheels were getting power, but the sound was ungodly. Upon inspecting the front driveshaft this morning, the Slip joint has side-to-side play, but not rotational play. I just did the U joints for the rear and didn't think about doing the front. Should I do this first or is the Slip joint toast? Or something else?
I will try to make a video for reference.
The specs are 77 CJ5 with a 304, T150 transmission, Dana 20 Transfer case and D30 front axles (all stock to the best of my knowledge).