No Wheels Were Balanced

Just because it idles smooth, you maybe assuming something here.

This is running up to 4500 rpm in first and second. Smooth.

It appears as of 40 mph (in both third and fourth gear) and gets more annoying at 50-60. It’s a buzzing kind of vibration. It seems to still be there in coast and neutral.

Sooooo, I measured the angles again.

All angles are going down from the front of the car to the rear.

Trans: 2.0
Shaft: 1.1
Diff: 0.4

This is as accurate as I could measure, measuring repeatedly and carefully as I could.

According to the Tremec app, this is fine.

Then using a magnetic laser

BFAAB333-55ED-4079-9156-ADA41005A1F8.jpeg 1350B7D6-31EB-4628-9EC3-93ADAABE4C1B.jpeg

Spot on.

The driveshaft, that I had to drop to check the angles, the U-joints feel just fine and no needles missing.

I will check the half-shafts... tomorrow. Those, as far as I know, are not balanced on C3 corvettes.

ADD - however, I do feel the vibration is too fast to be the half-shafts.

That leaves the transmission and the differential.

That being said I came across something curious o_O. The driveshaft to yoke bolts were not as tight as I left them. I won’t say they were loose, but they definitely were coming loose. And that’s the second time that happened. To me, this is a hint that the vibration is possibly coming from within the Muncie.

If it was the diff, I’d suspect I could rattle the pinion yoke around a bit in the bushing and I can’t.

Tomorrow I’ll flip the driveshaft 180 degrees in relation to the pinion.

Then I’m out of ideas.
 
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Hmmm. There is one last thing to test. Bringing the pinion angle from 0.4 to 2.0 like the trans.

I will remove the snubbed and place some rubber shims in there. I don’t want to trim it just yet. Let’s see what effect that has...
 
See, I told you swapping the wheels was a valid test.
And you got a result. Maybe not the result you were expecting, but none-the-less - a result.
 
Well, I put it in fourth gear, crawled under and eyeballed the output shaft. I could not see any wobble. This was at 1,000 rpm.

I’ll ask an assistant to bring it up to 3,000 rpm to see if I can feel with my hand a vibration inside the Muncie.

FWIW Another thing I noticed... I grabbed the pinion yoke and, whereas the doesn’t seem to have any lateral or axial play, it does seem to have a lot of backlash. It cracks quite a bit. I’ll try to measure in degrees but it seemed to be around 10-15
 
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