Well, I finally got enough pics to show how I shorten a drive shaft. It really isn't a difficult process but has several steps, so I will have to break this up to get all the pics posted. It usually takes about an hour to complete the process. Only drive shafts that are straight (not stepped or tapered) from end to end can be cut this way and I always do the cutting at the rear end.:rolleyes:
The first step is to insert the splined yoke into the tailshaft of the transmission and take a length measurement. I just let the back end of the shaft rest on the floor, push the yoke in as far as it will go, and then pull it back 3/4 inch. Turn the shaft yoke and the rear end yoke so they are in phase with each other. Now take a measurement from the depth of the rear yoke (where it normally holds the U-joint) to the rear of the bearing cup on the front yoke. This dimension will be the same as a center-to-center measurement, but is easier to get, especially if you are working alone. On my roadster it measured 17 5/8 inches.:HMMM:
Next, I remove the drive shaft and take a center-to-center measurement on it's U-joints. This 1986 Camaro shaft measured 41 1/2 inches. Now subtract the needed 17 5/8 from the existing 41 1/2; the difference of 23 7/8 inches is what I needed to remove from the existing shaft. Before I throw it in my chop saw and lop off the end, however, some pre-planning and preparation is necessary.:o
First step in modification is to clamp the uncut shaft in a vise and mark the position of the yoke and any weights that might be attached to the rear of the shaft. Note that the front and rear yokes are always in phase with each other, but since the shaft was balanced with the yoke in a particular position, I want to put it back together in the same position. I use a coarse file and "draw" it sideways the length of the shaft. This gives me a permanent mark that no amount of handling will erase (I learned this the hard way).:(
Next, I knock the rear weight off with a cold chisel and put it aside to be reattached later. Then I grind down the weld holding the rear yoke to the tube. I grind it until it is completely flat all the way around the shaft. This makes cutting through it easier and, as an added benefit, the grinding heats and discolors the end of the tube so I can see exactly where it stops.:3dSMILE:
Using the discolored marks as a guide, I cut all the way around the shaft about 1/16th inch deep. This can be done with a hacksaw, but I use an air-powered "whoopee" saw.:rolleyes: