drivetrain groan

88 AW4 np242 d35 162k

i've been having this problem since i bought my jeep.


I have a drivetrain groan of sorts that i can't seem to track down. I think i might have a worn or stretched chain in the 242. It happens in all gears at all speed and stays consistantly on the freeway. When pulling away from a stop i hear nothing until i reach desired speed then boom there is the noise, happens most frequently while coasting. Sometimes when putting the engine under load to maintain a speed it will disappear until i coast again. other times its a constant problem once up to speed. it happens like a light switch, its there then its gone. I can also feel it in my feet while driving.

things i have done to attempt to remedy the problem are few because i'm unsure of the source.

I have removed the front driveshaft and driven around and still had the problem. it seems to be a little less prevalant. I have drained and refilled the transfer case and the problem has remained. I can also spin the front driveshaft by hand while in park about 1/8 of a turn. While i had the shaft out the u-joints seemd to be ok. the rear driveshaft doesn't budge a mm while in park.

any other ideas to look for?

TIA

bump up for the back at work jeepers.

also was thinking mabye a trans mount gone bad.

sounds to me like a bearing is chunking. but its been doing it for 3 months since i've bought it without getting worse and nothing seems to bind up. also happens in full time and part time.