Hey, I drive an 89 with manual hubs. A friend and I did a break job a few months ago and used marine grease instead of bearing grease. The first time I locked the hubs in the driver side hub started popping in 4wd and out. When I unlocked the hubs it stopped. So we took the hubs apart and changed the marine grease out with hi-temp Red grease. It worked for a wile then one day when I was drivin down a loggin road the hubs started popping again. Do you have any idea what the sound may be, how to fix it and if or what I souhld replace.

 

Inspect it for damage: hub body, hub gear, and shaft splines. Also the CV joint side of the half shaft.