It is a VERY strong tranny...The only problem they tend to have is the 5th ger nut falls off and you lose 5th gear. My roommate has a 1998.5 24V cumming with an NV4500 and it lost 5th gear at 105,000 miles and we just put the updated nut in. Well The "updated" nut fell off again after another 5,000 miles. So he replaced the tranny with a rebuilt unit that has the updated nut, updated mainshaft and updated gear. IMHO, you really must replace all 3 to completely solve the 5th gear problem...
Chris