Driveshafts

I installed new U-joints and went to reinstall the shafts, when I thought I should double check which way they go back in. The manual says I should have marked them and re-installed them using my marks..... I took them out about a year ago, and didn't mark them.
So, does it matter witch way it goes back in? If so how can I tell witch way to put them back?
Thanks!

 

Doesn't matter, done 3 restorations and never marked a driveshaft. Front to back matters but not how its oriented on the yoke.

 

you do want them phased right though. meaning they need to be straight in line (the cups)

 

You have to separate them at the slip joint to get them out of phase though.

 

Didn't separate the drive shaft, if that's what you mean?

Just pulled them off and swapped out the u-joints..... rebuilt the tranny....and the front end....and the brakes.....

 

Thanks!

 

Yes, that's what Walt meant. If you don't phase things right you end up with some ineresting vibrations. My MB had some arrows stamped in to indicate the correct alignment.

 

wasn't sure if you did or did not separate the two. was food for thought

 

A very good thought oddfire.. You never can tell what a PO has done.

 

90% of the time it doesn't matter. It's the other 10% that gets you .
It's always best to mark the driveshaft and yokes and reinstall them in the same place. Sometimes on the assembly line there are issues with balance so the factory would balance them on the vehicle. Disturb this now you have a vibration. I've actually repaired driveline vibes by simply changing the phasing of installation on the yokes. Rare occurrence, but will drive you nuts trying to figure out the source of the vibration.

 

That brings up a good question for me. How much play is tolerable in the slip joint? Zero, some, a lot? any way to measure that if some is allowable?

 

As much as you can tolerate... IMHO

I have sheared shafts, but never had a slip joint fail, even though they were nasty.

I suppose highway vibration would eventually be bothersome.

 

I sheared off all the splines on a front driveshaft slip joint on my blazer years ago. I put 3 engines in it, 2 transmissions, about a dozen U joints and finally gave up when the tailgate fell on the ground after the back end rusted away. Wore that thing out in every single way.

 

Definitely. If you don't, the driveshaft has a tendency to "whip" and it can be very annoying as well as cause premature wear on the new parts you just put in. Yokes have to line up, especially if you have a multi-piece driveshaft. You would be surprised how many people don't know this. I used to teach and perform vibration analysis, and I don't know how many times I ran into this on older vertical water pumps in places like water treatment plants, where they used multiple driveshaft assemblies as couplings. The vibration could get quite severe. Have a good weekend...