Driveshaft alignment marks

[arizonajones]

Just throwing this out to see if anyone has experience:

 

In the Chilton (or any) manual, it says when you remove any part of the driveshaft, to paint alignment marks on the flanges that connect to the tranny, differential, and the u-joints so it all goes back together exactly the same. The Chilton manual says you need 'special equipment' to make sure all of these pieces are put together in the right orientation, so don't mix em up!

 

What if the PO of the vehicle mucked with it and didn't put it back the same?... Is there a DIY Ratsun method of knowing that the flanges and U-joints  are properly oriented to the tranny and differential? Or is it worth it to take it to a shop with 'special equipment'?

 

Thanks all.

[DanielC]

The "special equipment" is spin balanceing.  The transmission flange should not have any wobble, and the differential should also not have any wobble.  

If your truck has a two piece drive shaft, it was balanced at one time.  If the two pieces are taken apart, and not marked, it is possible that it was put back together with the drive shaft not bolted the same way it was, when it was balanced.

I believe a 521, even though it has four bolts at the connection between the two halves of the drive shaft, can only bolt together in two ways, not four.  A 720 is probably the same way.

 

Your options are go to a drive shaft shop, and ask about having the drive shaft balanced, or just go for a drive, including some freeway, unbolt the middle u-joint, turn it 180, bolt it back together, and drive it again.

 

There is also the possibility your drive shaft got bent slightly, by something hitting it, or getting high centered when off roading.  this would make the drive shaft vibrate also.

[datsunaholic]

I've replaced half of the 2-piece driveshafts many times and never had issues with balance.  It's possible the driveshafts were balanced each half, not as a full unit.  HOWEVER- a 521 has a slip spline in the middle of the front driveshaft, and THAT section was balanced as a unit.

 

As far as the connection at the front or rear flange, it only goes on 1 of 2 ways, and it wasn't factory balanced there.  Putting it on 180 out isn't going to hurt anything.  But if you replace U-joints, you want to get those ends on the same way.  But- because the shaft was balanced with the original U-joint, it will no longer be perfect anyway.  Close, just not perfect.

[arizonajones]

Awesome. Thanks guys. This is exactly what I was trying to understand.