Marking prop shaft before removal

[foster461]

Watching speed channel today while they pulled a tranny out of a truck. Once again I heard the importance of marking all the flanges so that the prop shaft goes on the same way it came off. The reasoning is that it is a balanced system etc.

 

I can see that the prop shaft end to end including both flanges might be balanced and that when replacing UJ's it might be important to keep everyhing oriented the way is was originally but I'm having a hard time imagining that the entire system (gearbox, prop, diff) is balanced such that putting the prop shaft on 180 degrees out of whack is going to make much difference especially when the TR6 drive shaft is not exactly long...

 

So I wonder what the truth is here, must the prop shaft go on in the same orientation that it was originally or does it make no real difference ?

 

Stan

[Andy Moltu]

It doesn't really unless the entire drive train has been dynamically balanced as as a single unit.

 

Probably the theory is that if it seemed in balance before it came apart then putting it back in the same orientation should maintain that.

[Richard Crawley]

Stan

Marking the flanges on removal to ensure they go back in the same orientation is good practice & always worthwhile but, as you say, the 6 drive & prop shafts are so short, together with the slower rotational speed of 15” wheels, I don’t believe it makes any noticeable difference at all & once you change the UJ’s, any dynamic balancing will be negated anyway! If anyone’s experiencing vibration on a 6 drive train, aside from the obvious wheel balance source, I would be inclined to look for a disintegrating UJ!