'02 Overdrive...Crunch Boom Clatter Bang
 

friend of mine has a 47RE behind a 6BT swapped into his Humvee, yeah, the actual military one, not the H1 or H2. anyway, the overdrive has apparently grenaded. not sure what specifically is broken but it's not good.

is this even common at all? are there any upgrades or replacements for the O/D-4th gear unit? this truck is sort of driven on the highway but it's mostly offroaded and abused, both in the mountains and the desert/dunes...

Sounds like the output shaft snapped. Are yo all sure its not in the transfer case?

no, it's not the shaft, still drives, I guess it just makes a pretty loud clicking noise cruising at 30-40 and decelerating from 35-15. just talked to him again after he looked through it some more, he thinks it's in the transfer case, for some reason this is the third T-case problem he's had in the last 15k miles. so if it's the t-case again, he's putting an Atlas in...problem solved, I guess. I'm interested to find out what the problem is, though.

I would be checking the linkeage on the case shifter to make sure it is allowing full travel and not coming back and allowing the case to slip inbetween levels.

have you checked the rear-end gears??? My unit broke 4 rear gears driving those POS's, thats exactly the sound they made, plus if the rear gear is damaged, itll still drive, just makes a lot of noise and you'll think its the trans or transfer case, id check it out