So I'm in the middle of installing a jwt clutch and flywheel. I am using this guide along with the fsm:https://my350z.com/forum/engine-drivetrain-and-forced-induction-diy/292139-diy-clutch-install-part-ii-jwt-clutch.html
This guide didn't mention to mark the driveshaft during removal, but when researching rear bushing replacement I noticed that it was advised. I also recently noticed in the propshaft section of the fsm it indicates to mark the positioning. Well I've already removed the drive shaft and I didn't mark it. How screwed am I? Is there any way I can get it to line back up right? The need to mark it doesn't really make sense to me personally, what would you do if you got a new driveshaft, shouldn't it be balanced independently?

 

You will be fine, I have forgotten 5 or 10 times over the years

 

Didn't mark mine 3 years ago.

 

all the clutches i have helped with, we never marked them

 

I think the drive shaft might have a mark on it from the factory.

 

I know that the drive shaft and differential pinion flange are marked at the factory to balance the run-out of the driveshaft with the run-out measured on the pinion flange. I assume this is to minimize vibrations at high RPMs.

 

I was worried about this too when I put in a different rear end. I thought how am I supposed to get the new rear end right when it hasn't been marked? Like everyone said it's going to be OK and would turn out to be OK for sure if you did pay attention. I think the key for you is to pay attention to the part where it says to put some pressure gently pushing the shaft up(?) when you are finger tightening the 4 bolts? That could turn out to be important too if it does really matter. Both are probably done to minimize any issue that could cause a problem.
Also there should be marks from the factory anyway- look one more time. And don't worry!

 

There probably isn't really enough manufacturing variation on these parts to really be noticeable, except at extremely high speed. All you need is a dial indicator and the service manual to redo the marks.

 

I did the same exact thing you did following the same exact post back in december. About 7k later and no ill effects