Shorten your own driveshaft, low buck style!
 

Well I am finishing out my last week in Austin Texas waiting to go in to work, so to pass some time figured I would write something up. I have been making my own driveshafts for awhile and until I went ahead and did it I considered it one of those " you cant do that at home " things. Not true if you are are confident in your welding skills. I have been doing them with a 110V lincoln SP135 mig and it has plenty of power to burn into the rear yoke. So here is a quick tutorial with a few pics from my last build, a 1947 cadillac model 61.

First off I start with a driveshaft that is obviously too long to be used. I will assume you have already figured out the length you need and are ready to shorten the driveshaft.

First thing to note is phasing. You want the front and rear yokes to be aligned in a straight line which is how they should be now. I do not have a picture of this but I pull a string down the center line of the ujoint cap one one end to the center line of the ujoint cap of the other end and scribe or mark the driveshaft tube and rear yoke along that line. That way after the rear yoke is removed it can be put back in line as it was. This driveshaft only needed to be shortened an inch or so and you can see where I used a sharpee to mark the driveshaft tube.
Use a hand held grinder and thin cutting disk to slowly cut away the original weld at the rear yoke. If you dont have a grinder harbor freight has them for $10 with a coupon, they work great. Once the weld is cut away this is what you get. Go slow so you dont cut into the yoke, you just want to get through the weld.

http://i34.photobucket.com/albums/d1...ps0cb16fea.jpg

Next you cut the driveshaft tube. I use a metal cutting chopsaw which gives a good straight cut. If you dont have one you can use the handheld grinder with a cutting wheel, just draw a cut line around the tube. Use a square to verify the cut it as square to the tube as you can get it.
Then tap the yoke into the tube with the caps phased as they were. Put the driveshaft in the car with the car in the air so you can work under it.

http://i34.photobucket.com/albums/d1...pse79b9dc8.jpg

Now here is where you get things straight. Info on the web says you need the tube straight to .005". Now either my eyes are really good or that isnt the real deal. I have tried putting dial indicators on the driveshafts but usually the surface is rough enough on the tube that I cant get a decent reading. So make a reference point. This one I took a piece of 3/8" steel tubing, clamped it to the rear axle center section, and used it as a reference.

http://i34.photobucket.com/albums/d1...ps53697161.jpg

Get the reference close to the driveshaft tube without touching. Turn the driveshaft by hand watching the clearance between the driveshaft and the reference, tap the shaft until it looks even all the way around while turning the driveshaft. Use a caliper if you want to double check but I have been good to go doing it by eye.
Get a tack weld on there when it looks good. You can see in this picture just how close I get the reference to the driveshaft tube. The closer it is the easier it is to see changes.

http://i34.photobucket.com/albums/d1...ps8b02f339.jpg

If all looks good after the tack weld put a few more on evenly spaced and double check again. You dont want it moving when you take the driveshaft out of the car.
Remove the driveshaft and weld it up for good. Get the majority of the heat into the yoke as the tube is not very thick steel.

Done! This one has been tested to 80MPH on the highway, smooth crusing. :-X22

http://i34.photobucket.com/albums/d1...psfa2c3e03.jpg

Good info, I never thought of installing it in the car to do the run-out check. My buddy always pulls the U-joints and rotates his between two spindles he clamps to his workbench.

Good report. I've never tried this with an automotive driveshaft that may be turning a few thousand RPMs but I have modified some tractor 500 RPM PTO shafts.
The last driveshaft I had built, they balanced it electronically by welding on weights.

Thanks, so far I have not had to have any of them balanced, I do not remove any factory weights and try not to cut where I have weights installed.

I had Homade's driveshaft balanced in the truck and he used stainless hose clamps to balance it, of course he has a machine to tell where to put the clamps to balance the shaft.

Nice job

I've shortened one or two in my day. I really like the nice and simple run-out method you use. Thanks for the tip.

Bobby

No problem, hope this gives someone the courage to go for it themselves.

Great write up... Thanks for sharing

Old time method... if there is no vibration don't mess with it.

If there is a vibration, put two hose clamps on it in the same spot. If the vibration gets better, try moving one 90 degrees. If it gets worse move it the other direction. Once you find the location with no vibration, tack weld them on.

I can see using hose clamps to get the balance right but I wouldnt use them permanently. Even a washer tack welded on would look better than that.