Posted by Charlie on September 27, 1998 at 19:54:57:
In Reply to: NP540/541 info. posted by Bob on September 27, 1998 at 19:05:08:
The NP540/541/542 were generally used in 1.5 ton to 2.5 ton trucks. There may have been a very few in the old great big W300s. In overdrive configuration, the NP540 has the following ratios: 6.06 (1st and reverse), 3.31, 1.81, 1.00, 0.82. In non overdrive configuration, 5th is 1.00, 4th 1.22, 3rd about 2.10, 1st and 2nd same as OD; but there are many other ratio sets for the non overdrive versions. The main difference between the 540 and 541/542 is, I believe, torque capacity. A 540 has a capacity of about 330 ft-lb and should be fine for any typical PW/M37 repower. The NP540 is the shortest heavy duty 5spd I know of. It is 13" front to rear of case. If you find an overdrive NP540/541/542 with ANY bolt pattern, if the gears are good, BUY IT!. If you don't want it, I do. Unfortunately, there are no new overdrive input gear/shafts around. It so happens that going up hills with a heavy load with the pedal to the metal is hard on input shafts/gears when in 5th gear. You can always switch the guts to another case.It's remotely possible that there is a case that bolts up to the PW or M37 bellhousing, since the flathead was used in heavier trucks. But if not, depending on the bolt pattern of your case, it shouldn't be too hard to machine out the input bearing retainer/index hole,accurately drill and tap 3 or 4 bolt holes, find a clutch disk with the proper splines and diameter, and shorten the little driveshaft. That's what I did with my Clark in my M37. 0.82 X 5.83 = 4.78. with 4.89s, it comes out to 4.01. Good ratios for repowers, with 40-41" and 35-37" tires respectively. The 5th gear direct versions would be worthwhile in a repower project using 4.89s and big tires, to give closer splits.
Charlie