A buddy gave me a driveshaft from a Camaro I intend to have shortened for my 33 Master coupe. It has a large weight spotwelded on the rear end and a smaller weight mounted at front of the shaft, both on the same side of the shaft. I wonder why a shaft even has to be balanced at all if the ends are welded on straight let alone a bunch of weight on the same side of the shaft. I'm temped to cut both of them off when I have it shortened and forget it. Any comments?
Yeah and it should need it. I have gotten away with balancing one in an emergency with a large hose clamp.
Try it. Worst That happens is take it out and have it balanced. The important part is make sure its phased correctly when you weld it back together, addind a few weights is easy. I'm gonna bet That you do decide to remove it and have it balanced.
Yes I'll will likely have it balanced but why so much weight on it from the getgo? One weight is 1X1/2 and the other is 1 3/4 X2"?
if there was such heavy weights on it i would ***ume the driveshaft needed it i'd have it cut AND re-balanced at the same time....but i'm lazy and only like to do it once. do it correctly the first time and save some work/expense/problems
Could have to do with the seam in the tube. More likely the irregularities in the unmachined portion of the forgings used in the ends.
A guy brought in a Dodge van driveshaft to balance because it shook badly after he changed u-joints. We had the slick Stewart Warner Driveshaft adapters that could pick up either the slip yoke (short shaft that slips into the trans), the various flanges, or U-joint caps. Spun it up and it was VERY heavy, right on the factory weights. There was a lot of tube runout at one end, with the high spot inline with the weight. We dis***embled the u-joint, rotated the shaft 180, and put it back together. Now the tube runout put the high spot opposite the weight, and minimal balance corrections were required. The yoke was machined badly right from the factory, and offset the tube. The factory balance weights were compensating for the tube m*** being way off center. When the owner had replace the u-joints he had not marked the tube and yoke positions, and had inadvertently installed the yoke 180. I'm not picking on MOPAR, but that was the only grossly mis-machined yoke I've seen yet. Max tube runout of a well built shaft should be on the order of 0.010 inch. For dynamic reasons the weights should be inboard about 23% of the shaft length, but welding weights there tends to bend (and unbalance the shaft) the shaft much more than end mounted weights. Some shops balance the driveshaft without u-joints running on the tube OD. Since centering and balancing go hand-in-hand that is pretty much a waste of time, since the likelihood of that being the spin axis in operation is just about zero. Plus the tubing is not particularly round, so makes a crummy bearing journal
A good friend had a driveline service in the bay area, Ca. Some guy brought in a driveshaft that had been lengthened to 68", wanted to have it balanced. Joel had just painted the inside walls and ceiling of his shop, hospital clean... The shaft was spun up on the big lathe and parting tool dug into the first weld, and Jing! Blood Red stuff squirted all over Joel, up the wall and all over the ceiling...Joel thought he cut his hand off! A quart easily, No...not blood. It was ATF! Someone had filled the driveshaft tube with automatic ****** fluid. (Balance???)
The longer the shaft, the more sensitive to imbalance and harmonics. Remember, it's spinning whatever the rear axle ratio times faster than the wheels, and wants to whip about the center axis out at the ends.
How short are you going? My friends dad built drive shafts for years at Fleet Pride and then became manager. Anyways I watched him build me a few drive shafts. If they are real short like under 2 feet there is no need to balance it if you build it straight. More important is having the u-joints phased correctly and having the correct pinion angle. I've shortened a few shafts on my lathe I just figure out a way to chuck it up then us a dial indicator to straighten it and weld it up. I use old yokes in the chuck etc. I'm not racing in those cars, and they worked fine. The ones I really need good I get from Tom Woods drive shaft way cheaper than the local Fleet Pride. I'm sure there are other out there I built a relationship with Tom. The hose clamp balance is in my manual drive train textbook you use 2 apposing so neutral and move them around until it feel balances. Just remember when running the drive shaft on the lift you wan the axle at ride height. ~Justin
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