Posted by Clint Dixon on Thursday, December 23, 2004 at 1:59PM :
In Reply to: Clint and picture posted by MoparNorm on Thursday, December 23, 2004 at 1:17PM :
One one point you are correct and I totally agree. On the other point you are...well, let's just say I totally dissagree.
Your quote,"it certainly does know when the ends are not parallel!!!" I totally agree with you on this.
You have raised a point that I did not cover in my long winded post. The axis of the transfer case output shaft, and that of the axle pinion gear, should always be parallel because the caps on the u-joints travel in an ellipse when these axis are anything but one and the same. The goal is to keep both ellipses exactly the same shape, otherwise vibrations develop. The only way to do this is to keep the two axis parallel. Also of great importance is to have the two yokes that the draveshaft attaches to in phase. Otherwise, the two ellipses will be conflicting one another, even though they may be the same shape. Again, vibrations will be the result.
Your quote, "As long as the input and output shafts that the yokes are mounted to are parallel, it make NO difference where they are located. The driveline doesn't know it is crooked". I totally dissagree with you on this.
Use your attached image as an example. The engine is offset to the right side. Now imagine the engine moved so it is offset 30 feet farther to the right. The driveshaft is definately going to know that is is trying to operate at angles far greater than it was designed for even if the two axis may still be parallel and the yokes may still be in phase. The ellipses that the u-joint caps are trying to travel through are going to be very pronounced.
The trick is to try and get the ellipses as minimal as possible, or closer to true circles. Anything more elliptical than a perfect circle is bad to varrying degrees depending upon the shape of the ellipse. Moving the driveshaft to the upper output shaft on the transfer case causes the ellipses of travel to be more pronounced than they are when the drive shaft is mounted where it is supposed to be. This does not cause the driveshaft to be necessarily "crooked", but the driveshaft is forced to speed up and slow down repeatedly during its revolutions at a greater ratio than when the axis are closer together. The drive shaft does "know" this and shows it with increased vibration and wear within the u-joints.
Clint
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