I just swapped out my 3rd member with a different one and it seems to have gone well minus a small leak and a slight wobbly sound with the same frequency as driveshaft rotation.

I've had my driveshaft out before and always made sure to put it back in the same way it was before it came out. This time I couldn't because this driveshaft yoke and pinion flange were meeting for the first time.

I don't know if this is my problem or not, but it got me thinking...

If the driveshaft is balanced, and there's nothing wrong with the differential assembly, why does it matter how they get connected?

 

Theoretically it shouldn't matter, but it isn't too much work to swap it 180 and see if it gets better.

 

i know its REAL important to mark relationship on a double cardian joint....i marked it but forgot to put it back together like that, vibration hell...but i traded the ford for my new dodge, so prob solved

 

i just swapped out my rear third as well and was wondering the same although i have not noticed any vibration. i would try rotating the drive shaft 180. the FSM does say to mark the connection (although not possible in your case).

 

The wobbly sound is still there no matter how I orient the driveshaft.

I'll try removing the driveshaft completely and drive around on my front wheels and see if it's still there. Not sure what that will prove though.

All I did was swap out the 3rd member. Ugh.

 

Are you sure the new 3rd is in good shape?

 

Not at all. Right now I'm thinking it's the most likely culprit.

The wobble is at the same frequency as my driveshaft's rotation. I know(?) the driveshaft is good. So it's got to be my used 3rd member swapper because the pinion inside it is the only other thing spinning at that speed. That's how it looks to me, as much as I'd rather it be something else.

 

I don't think the marks apply if you replace the U-joints with new ones, but apparently it matters when you use the old U-joints since they tend to establish a seat.

 

d-shaft/pinion(companion) flange orientation doesnt make a difference. The d-shaft is balanced by itself.. Just don't take the double d-shaft apart or remove the slip yoke without marking for reference..