3 Speed to 4 Speed Swap Questions
 

Hello, been a while since Ive been on here, work takes all my time, Ive been driving my 60 like crazy and getting ready to swap the motor out, (305 done wore the cam down) but i still cant kill it, Been driving it like this for months, it will pop back through the carb at high rpm, So im swapping in a 350 im re gasketing now, I plan to change out the 3 speed OD with a truck four speed, Its a c20 custom camper, Its a wonder i haven't grenaded the little 3 speed with all the abuse it takes, My main question is i now have a one piece drive shaft and i would need a two with the truck four speed, where would i mount the carrier bearing? I don't have a two piece drive shaft in my parts trucks so i may have to make one from a 73-87 truck work, Any info will be great, Thanks

Re: 3 Speed to 4 Speed Swap Questions
 

Why a 2 piece? All of the 3 and 4 speeds I have run have used a one piece.

Re: 3 Speed to 4 Speed Swap Questions
 

The SM420 truck 4 speed (and others like the SM465, NP435, etc.) does not have the slip yoke on the end of the driveshaft that goes into the trans, so the slip joint has to be in the driveshaft itself.

Re: 3 Speed to 4 Speed Swap Questions
 

Scratching my head...

Re: 3 Speed to 4 Speed Swap Questions
 

Yep, has to have a slip yoke to make up for distance when the springs are compressed with a heavy load it shortens the driveshaft distance, I'm just not sure where the carrier bearing mounts with the x frame,

Re: 3 Speed to 4 Speed Swap Questions
 

Check this picture out; no slip joint at the trans.

Not sure either, but I'd have to guess it mounts inside the "X"? Someone on here should have a picture of the OE setup.