As part of a new plan to wrest a little more control over the costs that can be involved with building a car, especially something of this nature, I decided to take a stab at shortening the driveshaft I picked up for Truckstang from the junkyard. Prepping the shaft is the easy part, but this is where the simplicity ends. Once the yoke is separated and the tube shortened, the next phase is to reassemble the yoke to the tube then check the runout on the driveshaft using a dial indicator tool. This tool has a plunger that rests against the tube on the driveshaft and as you rotate the driveshaft, the amount of wobble is translated to a reading on the scale of the indicator. If the yoke isn't true in the shaft tube, the runout or wobble will be excessive and show on the indicator and would even be visible to the naked eye.
Part of the dial indicator set is the magnetic mount that holds the actual gauge. This mount hangs or rests at some point under the car and has a couple arms that can be adjusted to place the indicator gauge at the desired point on the driveshaft (or other rotational device) so it will be stationary as the driveshaft is rotated. With the gauge situated in a spot that was satisfactory, which had the magnetic mount stuck on the front part of the differential body, the gauge was in position. When in the standby position, it doesn't read zero, but will require a light pressure on the plunger to get to the zero point. This way, the variations can be read below and above the zero point. If the gauge bottomed out at zero, if the shaft rotated away from the gauge, it would end up losing contact for a brief moment, giving an inaccurate reading. So with that bit of info, the gauge had to be pressed against the surface of the driveshaft tube to get as close to zero as possible. It doesn't have to be exactly at zero as simple math can help one figure out the variations in gauge needle movement to give the readings needed. At this point, I jacked up the right tire and put the transmission in neutral to rotate the tire and hence, the driveshaft. As I rotated the shaft, when the shaft rotated to the point where it had maximum pressure against the indicator plunger, I tapped the yoke lightly to try and "work" it a little, watching the gauge change. I then rotated the shaft again, checking the variation and repeating the same thing until the variations were small enough to put the reading within tolerance. Researching different sites had the runout at anywhere from 0.010" to 0.020". I had a runout variation of around 0.012", which was a middle ground compared to what others have stated. With that, I pulled out the welder and added four shitty tacks equidistant from one another around the shaft and yoke to hold things stationary. I checked the runout once again to confirm that nothing changed. Once I confirmed this, I pulled the shaft so I can do a finish weld with a more powerful welder. The little flux core is not the kind of welder that needs to be used for making this kind of weld as this thing needs to have a super clean and solid weld that can't be delivered with the flux core machine. Even after I weld the yoke in place I'll have to grind the weld slag to even everything out as any excess slag in any one spot can throw the shaft off balance more than it may already be. Once the welding is done on the shaft and the slag ground down and the shaft reinstalled, there's a matter of balancing. Now, this can go a couple ways. The common denominator here is that old heads would use hose clamps as the weights for setting the balance. Now, the more in depth method is jacking up the rear end and safely mounting the car so it can be put in gear and accelerated to highway speed or something close to it, or otherwise to the point that vibrations are noticed. One then takes a piece of chalk and holds it just close enough as the shaft wobbles to allow the shaft to knick the chalk. These marks are the points where the shaft is wobbling to the maximum point in that direction. This is done at the front and back of the shaft. The hose clamps are placed 180 degrees opposite from the chalk marks then rotated slightly as the driveline is run up to speed, doing this stop and go method several times until the driveline can be run with a minimum of vibration. Only then can the shaft be considered balanced. If this cannot be achieved then its likely something else is off. Maybe the U-joints are out of phase or the tube is bent. Either way, it would mean starting over from scratch. Hopefully we have everything true. I did read of other bootleg methods shadetrees used. One of my favorites is where one would drill a hole in the shaft, and inject oil into the shaft then plug the shaft. The oil provides a form of internal fluid balancing that may very well have to be utilized if our efforts at balancing fail.
0 Comments
Leave a Reply. |
Archives
May 2023
|