Hey there i was wondering if you guys could give me your thoughts... i curently owna 91 wrangler 4.0 with an ax-15 thats on its way out. I have 35' MT dana 44s and am along with the tranny i plan on swaping in a flipped dana 300 (figured i would spend less time measuring drive shafts if done all at once) is there anyone out there that have done either or and have input on this, im kinda leaning towards the NV 3550 just cuz there isnt much on the duriblity of the NSG-370, but i still like the deeper first gear and closer ratios. im to understand both swaps are about the same for me just need to get the relocated CPS for the 6spd which i could deal with.... just wondering what your thoguhts were.  

http://forums.jpmagazine.com/70/800033/jeep-transmission/<strong>six-speed-transmission/index.html</strong>
the torque ratings are close, I do like the closer ratio between 5 and 6th, the six speed has a .84 OD, if you have tall gears It'll help the 4.0 on down the road with the 35's.
the 3550 has a .78 OD..

you can end up with close to the same 1st gear crawl ratio and final drive by a gear change with either of the three units.  

jpmagazine also had an article on the nv4500, I have the nv3550 and pretty much the only thing I don't care for it is that when in nuetral and foot of the clutch it sounds like there's marbles down there and it's worse sounding on warm days.  It is normal for the nv3550 to do that do to extra clearances to keep from tearing up the transmission, or so Jeep says. Anyways here's the link for the nv4500  http://www.jpmagazine.com/techarticles/drivetrain/154_0604_nv4500_manual_transmission_throwdown/index.html  

ya the more i look the less i see there to be info on duribility with the 6spd. so ill just throw in the NV-3550 and if there is more info in the future ill think about the 6spd  

ya, durability info seems scarse, but they do use it behind the diesel that has 100ftlbs of torque than the tranny is rated for, I haven't heard of any problems yet.