Is a Miata drive shaft clocked?

Does the drive shaft in my NB Miata have to be clocked to the flange on the differential? Is it marked somehow, I couldn't see any markings when I had it out. Something is "off" in the back of the car. It feels like a wheel out of round, but the wheels and tires are fine and have been swapped for every set I own and the imbalance persists. I'm thinking something may be off with the drive shaft or axles.

Check the PPF alignment. You'll also find the driveshaft u-joints have a flat spot, they always do. I wouldn't blame them, though.

How can the PPF alignment be out, there's 2 bolts and 2 holes ? What can move?

Engine and transmission mounts, dead bushings, etc.

DeadSkunk wrote: How can the PPF alignment be out, there's 2 bolts and 2 holes ? What can move?

Slots, my friend. Slots. Loosen the bolts at the front of the PPF and you'll find you can shift the whole thing up and down.

https://grassrootsmotorsports.com/forum/grm/help-me-diagnose-my-miatas-vibrations/64126/page2/

z31maniac wrote: Engine and transmission mounts, dead bushings, etc.

The beauty of the PPF system is that the drivetrain does not shift around... the transmission and differential are fixed relative to each other with no bushings to move. The whole drivetrain only meets the body at the two motor mounts and two diff wing mounts.

So, I'll need to remove the drive shaft and get one of those protractor/level devices to make sure the flange at the differential is parallel to the one at the transmission?

No need to remove driveshaft. Just loosen the front two bolts a little bit. Use a floor jack under the tail of the transmission to set the proper height, then tighten the bolts.

I forgot about this adjustment myself. My car also has a 70mph vibration from the driveshaft area. I think I will try this soon.

Keith Tanner wrote:

DeadSkunk wrote: How can the PPF alignment be out, there's 2 bolts and 2 holes ? What can move?

Slots, my friend. Slots. Loosen the bolts at the front of the PPF and you'll find you can shift the whole thing up and down. https://grassrootsmotorsports.com/forum/grm/help-me-diagnose-my-miatas-vibrations/64126/page2/

This just jumped to the top of my To-Do List for today.

CGLockRacer wrote: No need to remove driveshaft. Just loosen the front two bolts a little bit. Use a floor jack under the tail of the transmission to set the proper height, then tighten the bolts. I forgot about this adjustment myself. My car also has a 70mph vibration from the driveshaft area. I think I will try this soon.

But ,how do I know what is the proper height?

Probably further forward from here:

Thanks Woody. As an aside.....I wonder how a Stancer would measure this after the frame rails are beat to crap?

Well, mine was about 10-12 mm low , so that's adjusted. It took less than 10 minutes to do, even on my 16 Michigan winters rusty NB.

I just did mine too. I'll post some photos tonight. Time for a road test.

Good thing for pictures... It was killing me trying to figure out what a PPF was...

I went for a 40 mile drive after supper. I never went above 60 MPH, but it certainly seems smoother so far. Tomorrow I'll try a run down I94 to see what it's like at 70 or 80 MPH.