Another bent driveshaft thread

hemi446 said

I didn't know you could straighten a driveshaft that is bent with a 1/4" to 3/8" out of round. That much of a bend should have been easy to see if the driveshaft is sitting flat on a level floor or a straight work surface. In the past if I break a rear gear or break a transmission I have always had the driveshaft checked and replace the u-joints. Even after that I did break a driveshaft pulling high gear at about 135 mph I lost both rear tires and when I got it stopped half the driveshaft was missing we never found it. It is amazing how much force has to be controlled by the driveshaft not just turning but the axle angle changing when you accelerate and brake most people do think a driveshaft can wear out but they do even on the street they can become worn out.

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You'll never seen .020 or even .100 out on a floor or table, and using the car is no good because the joints aren't 0.0 as for angle and as they turn the shaft moves just so slightly off center and the play at the slip yoke also makes every shaft seem off in the car.

However that should have been extremely easy to see when the person who is making the shaft went to balancing it if they ignored it when truing the shaft, a good specialist will know right away if he/she ignored the spec in the truing stage and didn't pick it up in the balancing stage, a shaft with an issue at the center is very evident during balancing , and the right machine you can balance it out, but you know whats going on, unless its like most shops and they hire a guy and there is no knowledge and they're using a computerized machine that can't distinguish issues and the operator is just a screen reader, kinda like a machinist of a cnc machine, it's not the same as the machinist of a manual machine shop.

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