AA Hayes

So my NV4500 rear casing has a pin hole in it and is leaking fluid. i am curious about what my options could be at this point. i have temporarily stopped the leak with some metal epoxy. either i replace the case, with a new case, or replace my tranny. i was wondering about putting in the allison 6 spd, but am not sure how it would mesh up with my truck. or putting a new nv4500 in it. i noticed it makes a knock coming out of 2nd after i disengage the clutch and knocks again when i engage clutch into 3rd gear. i was thinking this was due to running on low oil, so i got under the truck and saw a drip, found the suspect and temporarily fixed it. not sure how long it ran on low fluid so i am leaning toward a rebuild or new tranny because i dont want to have any serious issues on a long haul trip. thoughts and comments please.

the 6.0L comes with a 5spd, the 8.1L and duramax come with 6spd

thanks, now, anyone have some good and bad experiences with these?

i recently purchased on 04 2500HD, i am curious to know more about the transmission i have. its rpo code is MW3 which is the MAN 5 SPD, NVG, 109MM, 5.61 1ST, O/D. mainly i am wondering who build this tranny and how people have found it to drive and last. thanks