dont run it in 4wd till you fix it! Mine made a noise like that when I would start over a rock and the front axle would slip or jump a gear. One day I did it for a buddy to help diagnose and the chain came through the side of the case. I robbed the t-case from my wifes 89 (she dont need 4wd)
1979 CJ-7 with 258 inline 6, 3 speed, stock, nice soft top and cover. The body is in pretty good shape, there are a few rust spots and one bad spot under the license plate.
The spare tire mount is in good shape.
It doesnt run I was planning an hei distributer upgrade because I cannot get any...
check your u-joints on the rear driveshaft thouroughly aldo also could be in the rear axle, possibly a squashed crush sleeve letting the gear slide back and forth ( If it is the crush sleeve now would be a good time for a u-bolt style yoke upgrade I think it comes with the sleeve)