I have a 1959 CJ3B. I recently rebuilt the engine and everything has been running fine.

Last weekend while driving it around the deer lease, while in 1st gear (Hi) there was a flapping noise in the transfer case or transmission. I crawled under the jeep to determine if anything was hung up in the drive shaft(s) and found nothing.

It will drive fine. It does not make the noise in 2nd or 3rd gear (Hi). It does not make the noise in 1st, 2nd, 3rd (Low).

Anyone have any thoughts as to what is wrong and what I should do?

Corey