I'm an idiot. I admit it.

[Racer57]

For several years I've complained here about a vibration after 60mph. EVERYONE here told me it was the driveshaft angle. But, I wasn't paying attention, due to the shop that installed my Tremec several years ago had made a point of telling me everything was aligned perfectly. I've had a new driveshaft made, swapped tires,swapped wheels and even put new rear brake drums on.  Yesterday a buddy that does some serious drag racing stopped by while I had the Cuda up on my lift. He asked me if I ever found the problem. I told him no. He told me to get my digital angle level. I dropped the driveshaft and he put the angle on the tranny then the differential and said " Frikkin idiot, your differential is 4.2 degrees too low !" He had some shims, and after a hour or so, the tranny was 2.9, zeroed it out and dif was 0. Driveshaft is now 2.3. Took the car for a ride, got it up to 115 before I had to back off for a semi on the Interstate and it was smooth as hell. First thing I thought of was all the posts on here that I ignored and it made me feel like a damn fool.  Now I know better. Btw, he took this pic while I was watching for Cops ! 

[340Challman]

I feel your pain @Racer57 . I chased the same problem for years as well. Had the guy at the rearend shop that rebuilt the rear and driveshaft tell me that all of my angles were perfect and he didn't even feel the vibration. I knew I wasn't imagining it. Finally, when I was putting the car back together after the restoration, I found the angles off. 

What I learned was to trust my gut. Even though I had checked everything else myself. I allowed someone else to convince me that it couldn't be the pinion angle when it was all along.

Glad you found it. Enjoy that smooooth ride. 

[RUNCHARGER]

Glad you finally found it. Too bad you didn't enjoy the car fully for that time. I don't even trust my own work anymore, I double check everything these days it seems.

[Katfish]

Glad you found it!
Can you provide more details on the process?
You mention "dropped the driveshaft"?
Can't you measure everything with the DS in?

[Bullitt-]

  Congrats for getting this solved & for being MAN enough to admit your mistake.. 

[Racer57]

Glad you found it!
Can you provide more details on the process?
You mention "dropped the driveshaft"?
Can't you measure everything with the DS in?

Dropping the driveshaft makes everything a lot easier to access. You also need to take shocks off of plate. Put digital angle on tranny. Mine was 2.9 degrees. Then zero it out. Then put it on the yoke of dif. That will show the difference. Mine showed 4degrees down. Ideally you want zero. I put a 4 degree shim between springs and axle. put everything back together. tran was 2.9 and dif was zero.  Installed driveshaft and it showed 2.3. You want 1-3 degrees.

[captcolour]

Driveshaft is now 2.3.

How do you measure the driveshaft to get the 2.3?  Couldn't you have done that first to see it wasn't between 1 and 3 to know you have a problem?

[YellowThumper]

Not so much an "idiot", more of someone who trusted another professionals opinion.
Glad to hear it is now sorted.

[Racer57]

Driveshaft is now 2.3.

How do you measure the driveshaft to get the 2.3?  Couldn't you have done that first to see it wasn't between 1 and 3 to know you have a problem?

Level was placed directly on the driveshaft. I honestly can't answer if doing it before the work what it was.  I'm sure I had done that in the past. But I don't remember the results.

[Spikedog08]

That's a great store!  Super cool!  I could not of found that . . What kind of level and put it where?    Put shims where?

[Racer57]

That's a great store!  Super cool!  I could not of found that . . What kind of level and put it where?    Put shims where?

Level was a 6" digital metal level with magnetic topside that I've had for a very long time.  Pictured isn't the one I used, but it will work.  First placed it against tranny end where output is, then against the yoke ends where clamps go.  Shims go between the springs and axle. I haven't looked, but I assume there is a youtube video of how to do it.