One piece driveshaft for 4/6 lowered 1968 Chevy C10 short bed?

[HeavyHauler]

Is anybody running a one piece drive shaft in a 1967-1968 Chevy C10 Short Bed that has been lowered maybe 4 inches in front and 6 inches out back?

I am wanting to replace the factory two piece system as I think one of the bearings is going out and I have wanted to go to a new one piece anyways.

[Keith Seymore]

I always prefer a one piece shaft.

Most squarebody short beds were one piece, with rare exceptions, so I would think a reputable shop could whip one up for you.

K

[HeavyHauler]

I wonder if any modifications are needed to the chassis or crossmember in order to run a one piece driveshaft after the truck is lowered?

[68panelman]

I thought all short beds were one piece?, every one I ever had was, including my current one, a stock 67.

[Tx Firefighter]

Originally Posted by 68panelman

I thought all short beds were one piece?, every one I ever had was, including my current one, a stock 67.

I've had quite a few short beds over the years. Some came stock with one piece, others with two piece. It depended on the drivetrain and differential ratio as to which it was built with.

[68panelman]

Thanks for the info Kevin, figured since my 67 has the tiny SM318, any other combo would definitely still have a one piece. Always learning

[SCOTI]

All of mine have been one piece shafts. My old roommate had multiple trucks w/2pc shafts so it boils down to the combo it came with from GM.

The 1pc shaft will work/fit w/a 4/6 drop. Driveshaft OD might make it a tight fit @ the upper portion of the front T/A mounting x-member hoop.

[Myself]

The last one I did we just went to the local junkyard which had an old pickup bed full of driveshafts. Measured up one the right length, got new U-joints, and installed it, no issues.

[1971Stepside]

I have one in my 71. No modifications to the frame were necessary.

[72LB]

Make sure your angles are good. I recently swapped to a one piece (2/4 drop) and had to adjust the pinion angle 4 degrees.

[Keith Seymore]

Originally Posted by 68panelman

I thought all short beds were one piece?, every one I ever had was, including my current one, a stock 67.

One piece vs two piece has to do with the driveshaft "critical speed", the point at which it begins to swing like a jump rope.

It is affected by length, outside diameter, wall thickness, material, mass and rpm. Highest shaft rpm is affected by vehicle top speed, rear axle ratio and tire diameter. Length is affected by wheelbase and driveline configuration (trans length, t case, etc).

The driveline is also affected by any unusual or unpredicted system resonances, which can crack a Tcase or some other failure mode even at a speed lower than the critical rpm.

From an OE perspective the driveshaft choice (one piece vs two piece) can be manipulated by controlling any one or more of those variables. Vehicle top speed is limited by several different components, including tire speed rating or driveshaft critical speed. Sometimes the driveline is the designated "fuse" (as directed by the program team) and speed is controlled through the use of fuel or ignition cutoff or some other ECM parameter, in order to maintain a one piece system as a cost save or warranty avoidance.

K