The Stovebolt Site Forums The Parking Lot '60-'66 Trucks will a SM420 from a 1962 C40 fit in a 1962 C10?

both have the same engine 235 but the c10 has a 3 speed in the floor manual.

reason im asking i got a completely rebuilt SM420 to go in the C40 there is nothing wrong with current one in it.

i wanting to put the 4 speed in the c10 because the transmission in it is so weak and it grinds in every gear.

what mods do i have to do with the c10 to put the 4 speed in it??

thanks Jake.

The biggest problem is the Floor Hump. The Factory 3-Speed truck will have a Low Hump on it and the truck 4-Speed requires the High Hump. That reason alone has made me decide not switch some of them through the years. If you have a good garage, a welder and a good High Hump Floor section available, it would make it an easier project.

I believe you would also have to change the Bell Housing as the 4-Speed trans should require a larger Input Shaft Housing Opening. You also may have to change the length of the Drive Shaft.

Bill

the frt brg retainer did not get larger until the advent of the sm465 ,1968 I believe
ron

I agree w/ Ron, the 3 speed front retainer changed in 68 too, which would have been co-incident with the 4 speed and bellhouse change .... I'd say the only problem Jake faces is the floor pan

Bill

but only in the trucks. passenger car remained the same
ron

so all i have to change is the floor hump? if so that is better than i thought it would be. my cousin has a parts 63 C20 with the large hump floor and im good with a welder so this shouldn't be any problem.

also i think the 4 spd should work well with the c10 since i believe it has a 4:10 rear might give it extra oomph hauling wood.

thanks gents! Jake

I think a big problem will be the drive shaft. The 4 speed probably has an emerg. brake on the back. If you have the shaft from the donor truck you could have the front part adapted the the 3 speed shaft.