I have a 1968 F100 long bed 2WD that originally had a 240 inline-6 and 3-speed manual. The 240 was blown up, so I’m swapping in a 302 with a C4 automatic.

I’m trying to figure out the best driveshaft setup to run — either keeping the factory two-piece shaft with a carrier bearing or converting to a one-piece shaft. Since it’s a long bed truck, a one-piece would end up very long. Maybe too long.

From what I understand, the factory front shaft section from my manual-trans truck will not work because it’s yoke-to-yoke, but the rear section should theoretically stay the same length since the carrier bearing location and rear axle position are unchanged. Unfortunately, my rear section was bent at some point (looks like forklift damage), although I can probably have it re made easily

My main question is:
Can I source or order the correct front driveshaft section from a factory 302/C4 long bed F100 with a carrier bearing setup? Or is there a better approach people usually take for this swap?

I don’t have the C4 physically installed yet since I’m waiting on an engine but would like the truck driving ASAP. exact measurements are difficult right now but I could maybe tell the shop to make a factory c4 length shaft with appropriate connectors.

 

I would wait till you have the engine set in place and measure yoke to yoke. You really need 3 measurement if possible, ride, full up, full down. Your looking for the shortest distance.

Most shops can make up what ever length setup you need. The problem with drive shafts is the rpm that is required vs length. So this is highly dependent on gear rations and tire size. I had to have a custom drive shaft made for my build, It required a custom carbon fiber shaft to be made (custom order/build) to get the length and cross section. The shaft is 84" long and cost over $2k, I'm limited to 5500rpm on my shaft before it will self destruct. The wall and dia is the sames sized used on 2000+HP drag cars. Drive shaft shops have software that they used to determine what dia, material, wall thickness is needed. It's the rotational harmonics that cause the problem. Once you get to a certain size/length they will self destroy them selves.

 

I understand wanting to get it back on the road asap but as mentioned, I'd wait until you can measure. It's not something you want to get wrong or make do with what you have.

 

I think you'll be okay with a single shaft
What's the wheelbase?

 

I'm not super familiar with these but the shaft length i believe is going to be pushing 60+ inches which is about the max for a single steel so it'll be a 4 inch and probably require a slip yoke mine is a bit longer wheelbase and transmission with a transfer case and they said I'd have to use an aluminum with a slip yoke ($1550 I think was the quoted price) for anything past 65 if I remember correctly (i think mine was 68) however my excessive off road time and the many times I've dragged the yoke through the dirt meant I went 2 piece steel and had to make it myself since the companies I called wouldn't make 2 piece driveshafts and nobody would make one single with steel as its not a difficulty thing its just physically impossible for a steel shaft to survive that.

Nothing super helpful here just the struggles I went through doing mine after I bought a new vehicle found out the ujoints were welded into the yokes and then spit the driveshaft. It was like $750 to make it myself so highly recommend seeing if an off the shelf unit can be sourced probably from a chevy as you probably don't have 1330 ujoints that make sourcing things difficult.

Also as far as getting the lengths you absolutely have to get it assembled and get the length before you buy the driveshaft they dont have a lot of wiggle room for the wrong size parts.