4x4 1/2 T vs. 3/4 T Drive Shaft - Same?

[Ironhorse]

Looking for an answer since I have no idea. Is a rear drive shaft from a 1/2 ton 4x4 LWB verses a rear drive shaft from a 3/4 ton 4x4 LWB inter-changeable or compatible? Have a shaft from my 1/2 ton 4x4 for sale on the parts board and a fellow member is interested but is looking for a drive shaft for his 3/4 ton 4x4. Will the shaft I have work for him? Both trucks are '71-'72 sm465/np205 set-ups.

[ERASER5]

U-joint is a different size most likely. Mine was. The length might work, might not. The 3/4 ton sits taller than the 1/2 ton making the D-shaft slightly longer. Think of a triangle with the hight being the truck, and the length being the linear distance from the front U-joint to the axel. The d-shaft is the hypotenuse. As the hight get taller, the d-shaft get longer. The slip joint can only absorb so much difference. On my truck, I am hoping the new springs will give some lift so I don't have to cut my d-shaft. I only have a bit more than a 1/4 inch of movement in one direction.

[argonaut]

Its also dependent on powertrain and towing capacity. The more powerful the motor the larger diameter, or thicker the walls or the driveshaft to withstand the torque. Same thing for u-joint sizes. And same thing if you are hauling/towing heavier loads, the drivetrain is subject to greater forces and torques.

[odog]

I took the drive shaft from my3/4 ton 67 and put it in my1/2 ton 69. No difference. Both were 4x4. The 3/4 ton had an Eaton rear end with an sm 420/221 trans transfer combo and the 69 had the same trans transfer combo but a 12 bolt rear end. No problems, the drive shaft was a 2 piece with a carrier bearing.
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[budman k20]

I have never seen a 2 pc driveshaft on a 4x4? Must be pre 71 technology. I know for a fact my 72 3/4 4x4 has larger u-joints than my 71 1/2 ton 4x4. Same for the front shaft as well.
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[mud.man.rj]

I have done it before and believe the ujoint size was different so I used the combo joint which is 2 different cup sizes so fits shaft and fits pinion.

[Ironhorse]

Thanks for the replies on the drive shaft question. Seems like others have done it but does involve using differant u-joints. Will PM the interested party and let him decide. Again, thanks for the replies, always learning from this board.

[odog]

Sorry, I forgot to say I used a combo u joint on the rear end, everything else was the same though.
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