Posted by Keith in Washington [162.158.107.202] on Tuesday, January 12, 2021 at 11:36:36 :
In Reply to: transmission education posted by Galen [173.245.54.194] on Tuesday, January 12, 2021 at 07:25:53 :
The NP420 and SM420 are completely different transmissions. The SM420 is a GM transmission with a great reputation that is very strong and has a very low 1st gear. 2nd gear is also synchronized in the SM420 and not in the NP420. I have an SM420 in my carryall.
I swapped an M37 NP420 into my 51 ffPW. It was a direct bolt in to the crash box bell housing. As stated below you need the center hump and passenger floor sheet metal and parking brake lever (actually just the lower mounting tang) from a later ffPW that had the NP420. Your PTO will not work in the NP420 as yours was designed for a spur gear transmission and the NP420 has helical cut gears. The PTO shift lever is also different.