prop shaft alignment quick test

I had time today to do a quick check of the alignment of my  prop shaft, or rather where the prop shaft goes, as I have it out right now…

I have to reiterate, this was a quick test, approximate measurements only. I attached my laser alignment jig to, in turn, the transmission output flange, then the front diff. input flange. Each time I measured down from the centre of the opposite flange to where the laser dot was. I also measured the distance between the centres of both flanges.

I did not measure any lateral alignment this go round.

What I found was the front diff was pointing down at a lesser angle then the rear transmission, 2.45 degrees vs 4.45 degrees. Ideally the angles should be equal and less than 4 degrees (but not zero degrees).

Here is a diagram of my results:

If you slept through trig, what you need to know is the TOA part of  SOHCAHTOA. TOA means tangent = opposite over adjacent. For example in diagram above, for transmission flange, the tangent of the angle is 100/1285 -> 4.45 degrees. Just do the 100/1285 bit on your calculator then hit the tan-1 button.


Here is a diagram of how U-joints can be oriented:

You can see how my syncro is in the “W” bend form, but the 2 angles are not equal. The angles must be equal, or damn close, to eliminate vibrations. This means I have to adjust the angle that the front diff. sits by shimming the front mount.

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