Hey guys, I have a idea of a build that I would like to do. I was thinking on it last night which brings me to this question. What are the deciding factors for using a solid rear driveshaft or split with carrier bearing.

 

Length.

Too long of a driveshaft would require a shaft that is so thick and so large that it will whip, not balance, and become weak.

 

X2 on that ^

depending on your joint you use, you can split it also to get a better breakover angle, but that's a minor factor on a long truck

 

The truck I'm thinking about would have a 140" wheelbase. My F250 has a 134" wheelbase and it is a solid shaft. Would the 7" difference necessitate a split shaft? If so whould I be better with split shaft or divorcing the t-case to keep a solid?

 

I couldn't tell you on the extra 7 inches, but divorcing is nice if you are going to have a decent amount of lift (some people like it...). Not sure what you're using the truck for, but for a trail rig, running a divorced t case, and splitting the difference of the front to rear axles makes it easy to keep spare parts on hand, being that the front and rear shafts can be the same length.
So what's the truck for?
Just some insight.

 

I need a bigger truck. All my trucks are single cabs and I don't have enough room as is. Two kids now with one in the oven. Looking into throwing a crew cab onto my 89. Maybe with a bronco back half too. Always wanted a four boor bronco. Going over all aspects of this conversion. The truck is my work truck ( construction ) so it would be a dual purpose rig

 

I like this idea, and especially the concept of the remote mount case with equal length shafts.
Carrying one spare driveshaft that can work for both the front or rear just has "killer" written all over it.

 

One more question. What are your thoughts on splicing two frames together. If I go thru with this 4 door bronco, I have to make some frame changes. Well there are three different ways it could go.

Option 1- Cut a 350 crewcab front and bronco rear frame and splice them together. That would put a splice right where the end of the crew cab would be. This option would require no body lift and would have the option of the keeping the rear fold down seat, though I want a full bench right now. I'm leaning towards option 1 and 3. Option 1 seams ideal with more chance of error. Option 2 slightly less ideal bet less chance of error. What do you all think

Option 2- Take my stock frame and weld ( scab ) a 7" section under the cab. Then modify the floor of the cab towards the rear kinda like a channel job. The truck frame doesn't quite work with the bronco rear tub. I could add a body lift to lessen the ammount of floor modifications needed.

Option 3- Take a crew cab frame and shorten it. The centurions were shortened right where the front of the rear leaf spring hanger was. I believe no body lift would be need this way but something might need modified with the floor.

Anyway I go about this there would be a weld seam in the frame. I know if I weld the frame like that it will alter the way it twists there. Was thinking of a fishplate on the outside and box the inside a foot to each side of the weld.

 

If you trust your welding/fab ability (tackling this project, I'm guessing so), I would think that option 1 would be optimal, but that's just a shot without personally knowing all the specifics.

splicing the frames with a long diagonal cut ( ###/ /### )

And a big fish eye over the butt weld ( <> )

And I say they are just as strong if not stronger than when you started. I've seen stake bed trucks, and roll back tow trucks extended like that, and watched them being worked without a hiccup.

 

Where the heck have you been Andrew?!!!

 

ha, I've been around..
made a temporary boy-cot of FTE after some admin run-ins, but, I missed it. Don't have a Ford at the moment, rocking a HEEP for now. You can tell how long its been by the sig, STGs Minions haha

 

Don't know if you caught all the BS that happened with the STG meltdown, but shoot me an email so we can catch up!! p4u1@msn.com