Okay, maybe some one can shed some light on this for me.

Why does my '50 long bed F-3 have two sections of drive shaft?

Why does the longer back section telescope?

What is the benefit of this? Did Ford do this on all pick-ups of the era?

I'm just curious if anyone knows why they were built that way and when the change was made to the modern setup.

 

I don't know why but the ‘69 long bed frame I have under my 55 originally had the two-piece drive shaft as well. Could have been that longer beds carried more load and the two-piece shaft may have been stronger, I don't really know, just a guess.

 

It eliminates drive shaft flex. By making a steel tube too long and putting torque on it, it begins to flex and twist. By putting a carrier in the middle, the length of the shaft is effectively reduced and the shorter shafts take much more torque to begin to flex.

Tyson

 

Well, atleast I know that there were others out there. I forgot to mention that the backend of the front section is supported by a cross-member. Maybe it gave better ground clearance on the longbed.

 

I don't know if it handles torque better because the previous owner broke mine.

 

I understand the Torque issue, I guess now drive shafts are stronger and can be made longer?

What about Telescoping?

 

I know ford has had the two piece drive shaft for a while, and still used it up until at least 1979. My 79 F-150 with a 351M had the 2 piece, while my 79 F-100 with a IL-300 had a one piece. I'm assuming that the 2 piece is suppost to handle more torque. I'll probably be modifying the 2 piece design off my 79 to be used on my 1952 F-3,

Jon

 

Probably telescopes for the suspension. All driveshafts have some play in the tranny yoke.. I'm guessing that your driveshaft from the tranny is mounted fairly solid... so if the second one didn't have play, the suspension and drivetrain would bind.

That is just a guess, I could be wrong.
I work with a few monster truck racing teams from time to time... they all use telescopic driveshafts, you would be suprised how much the driveshaft will actually extend, especially if the suspension geometry is a little off. But then again, on those trucks they can have anything from 20 inches of suspension all the way up to 3 feet.

 

It serves 2 purposes, one to eliminate shaft slap and rapid U joint wear and the other is to maintain a workable pinion angle over a wide range of spring loading and flex.

 

Nathan,

I have a spare drive shaft I won't be using if you need one...

 

I'm planning on using the F-1's drive shaft. But thanks anyway.

 

They had them in '41 (and probribly '40) also, on the 3/4 ton and up trucks.

I've seen some newer trucks with the same setups, some even with 3 sections.

Clayton

 

A universal joint, also known as Hooke's Joint does not transmit the same RPM from input to output. With increasing angle, the worse it gets. Multiple driveshafts reduces that angle, reduce the torsional effects, and also allow a smaller diameter shaft to be used.

A slip joint is necessary as 286merc said to allow when the suspension allows the rear axle to move up and down, the distance between the trans and the axle is going to change and there must be slack. The slip joint is usually in the transmission on cars, but on larger trucks with heavier transmissions, higher torque, and normally a emergency brake on the transmission the drive shaft is rigidly attached. Large trucks made today have 3 or maybe 4 driveshafts depending on WB. Check out a 26' Ryder truck.

Also as an aside because a U-joint is not 1:1 transmittal, that's why they couldn't use them on front wheel drive because the car would pull one way or the other, so the CV (constant velocity) joint was used.....