What goes into a driveshaft build?
This project is an example how a typical driveshaft is fabricated.
The vehicle is the boss's parts chaser - a 1970 Chevy C20.
The old 350 engine was tired, and the TH350 transmission was toast. The truck recently received a 383 stroker and a fresh TH400.
The TH400 is longer than the TH350 and requires a different slip yoke. The old driveshaft always had a rumble, and this was the perfect excuse to put down our beer cans and make it right.
This C20 has the Longhorn option that adds 6" to the wheelbase and the box. Notice in the picture above, there is an additional section at the front of the box giving it an overall length of 8-1/2'. This truck has a two piece driveshaft because it is a fleetside with an extra long wheel base.
Basic two piece driveshaft configuration.
After salvaging a couple of parts from the old shaft, a new shaft was built using a mix of new and used parts. The midship stub shaft, carrier bearing, and midship yoke were re-used.
After taking some measurements and doing some math, a piece of DOM (Drawn Over Mandrel) tubing is cut to length. This driveshaft will be made using 3" diameter, 0.083" wall tubing. The tubing is trimmed and ends prepared on our lathe.
A new U-Joint is installed in a weld yoke. The yoke and the midship stub shaft are fixtured into a press. The Ends are pressed into the tubing and prepared for welding.
Non-contact sensors measure runout and adjustments are made.
The tubing is tack welded to prevent movement.
The tubing is welded to the ends using automated computer control.
After the ends are welded to the tubing, and everything has cooled to room temperature, the shaft is measured for runout.
The forward shaft is now ready for the carrier bearing.
The transmission slip yoke is installed and the forward shaft is sent to the DL-500 balancer. More on that later.
The forward shaft assembly is complete, The rear shaft is built next.
Measurements are made, we do some math, and a piece of 3" diameter, 0.083" wall DOM tubing is cut and trimmed on our lathe. The weld yoke, splined stub shaft and tubing are fixtured and pressed.
The shaft runout is measured with computer controlled non-contact sensors and adjustments are made.
The weld yoke and splined stub shaft are tack welded in place to prevent movement during the automated full weld process.
A computer controlled automated process makes the full weld.
The rear shaft is allowed to cool to room temperature, and measured again for runout. The shaft gets a slip yoke, and is ready for balancing.
The shaft assembly is ready for balancing. The two piece driveshaft balance takes several steps to complete. The first step is to balance only the forward shaft.
The Hines DL-500 is a dedicated driveline balancer that determines inbalance and pinpoints where adjustments are needed. Weights are temporarily placed on the shaft with tape.
The weights are welded to the shaft, and allowed to cool to room temperature. The balance is then verified.
The rear shaft is mated with the forward shaft and balanced as a complete assembly. Temporary weights are taped to the rear shaft and placement is verified.
The weights are welded to the rear shaft and allowed to cool to room temperature. One final spin checks that the balance is within spec.
The balance weights are all in place. The driveshaft is ready for paint, and vehicle installation.
This particular C20 has an inverted crossmember with a unique carrier bearing. The installation is like a rubik's cube puzzle.
The Sonnax Chrome Moly transmission slip yoke is inserted into the transmission.
The carrier bearing clamshell is manipulated into the crossmember one half at a time.
The carrier bearing is bolted to the crossmember, and the rear shaft is installed.
The truck is back on the road and chasing parts. The 383 has plenty of power and the new driveshaft is solid and smooth.