Shorten a driveshaft

[Ken/Alabama]

I’m shortening a 33-34 torque tube and driveshaft for a customers 32. Torque tube is already cut to 53 1/2” total length. With the torque tube standing on its end it measures 50 7/8” from the floor to the center of the speedometer gear window. I’m thinking that the important measurement for the driveshaft has to be from the pin hole at the pinion to the center of the speedometer gear but I put the pinion in the driveshaft and temporary pinned it then measured from the leading edge of the double cup pinion bearing race up to where the front stub shaft should be to give me 50 7/8” to the center of the speedometer gear. Is there anything I’m missing here before I cut the tube ?

[30Murray]

I would bolt the torque tube up to the banjo with the drive shaft pinned in place then measure how much to cut so the drive shaft is 1/8" inside the front face of the torque tube bell. I believe that is the right amount and the speedo gear will line up with the hole. When I had mine shortened a few years ago I instructed the shop to shorten both the same amount. In my case the primary measurement was the torque tube length because it had to bolt up to both the banjo and a '39 transmission. You may be working with a different setup though.

[mercman from oz]

[cas3]

Generally speaking, you would take the same exact amount from both drive shaft, and tube. I've done several, here's my take on it.

I do the tube first. I like to cut the tube in a lathe at the rear where the original ford weld was. If you don't have a big enough lathe, cut it with a torch and then face off the forged end in the lathe and thats true now. Its thick enough you can even machine a step in it to fit the inside diameter of the tube while its chucked up.

Done even with a small lathe, steady rest set up for the cut at the rear will be the guide to weld it back true once you have your length figgerd out.

I've seen folks get away with just clamping it in a piece of angle iron, but I prefer to machine it.

For the length of the shaft, every Ford diff I have ever had here, many, the bevel on the transmission end is proud if the bell on the tube. No science here, lay a straight edge across the bell, the splines will be at the end of the bell with the bevel portion sticking out proud.

Iron trap garage, and our friend Mart both have youtube videos on the subject

[Brian]

Ken, you haven't said where you shortened the torque tube...will the radius rods still bolt up?

[Ken/Alabama]

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Originally Posted by Brian

Ken, you haven't said where you shortened the torque tube...will the radius rods still bolt up?

Yes , it’s been shortened and I also relocated the anchor tab in the center where the radius rods come together.

[cas3]

Ken, a guy like you must have some solid shafts around, bolt the tube and a solid shaft together and mark the shaft where you like it to determine length