Almost a statistic
 

Was out in dad's whip picking up water from a spring 10 miles away. On the return 2 lane split 55 posted limit car pulled out of a business establishment right in front of me. It was either smash them at 60 or leave the roadway. Miracle I didn't go head on with oncoming vehicles. Car took it well under emergency handling situation.

Made it out okay had to get checked in ER after getting the vehicle out and home.
Reason I'm posting is this:
Post off road testing while driving revealed a "harmonic resonance" in the clutch pedal and shifter while at constant speeds higher rpm in lower gears most notably 2 and 3. Now I'm a little pissed as my dad and I built this car 14 years ago with him currently being 80 he can't "get after it" like he used to. I don't think the car did it prior to the incident. Any ideas where I should start looking? It's not in the tires as it won't do it with the clutch depressed.
THANKS,
Chuck

A scary moment. I'd check underneath the car to see if anything got bent or damaged, maybe the driveshaft took a hit.

Bent driveshaft?

Maybe some vegetation (looks like corn) under the car in the clutch and shifter mechanisms, or damage to same?? Or damage/debris to the exhaust system or driveshaft?

When I was 16-17 I had a similar episode. I was on a two lane road, it was raining. Speed limit was 45, I was going about 50. A woman entering the road from my left waited until I was right up on her and then pulled out in front of me. I got on the brakes, trying not to lock up. I started to fishtail to my left, into oncoming traffic. I corrected and got back in my lane but then ended up having to go off the road to the right into someones front yard. My car stopped about a foot from a very large tree.

Glad you’re OK and that beautiful car didn’t encounter a worse fate. Love those 66 wheel discs. Hopefully you can get the vibration sorted soon.

Almost a statistic
 

Guys thanks for the concerns.
I went all over this thing yesterday.
Not even a scratch on those wheel discs let alone under the car.
The vibration only occurs with the clutch out.
Wierd.
THANKS,
Chuck

Bent rear control arm or torn bushing, or broken trans mount or bent crossmember? Something that could change the pinion angle or working angles of the u-joints?

Exhaust pushed around to where it can rub on something it didn't touch before?

https://i.imgur.com/TaSqCgMl.jpg

From this picture, it seems like the car would have been riding "high" as you went off the road. When you reached the bottom of the swail, and hit that rise just before the corn, you would likely have bottomed out and all the important stuff under the car would have hit the ground with significant force. It also appears from the tire marks that you were going at least slightly sideways, not straight. Something is buggered up under there.

I had a bent rear axle housing. Ck it.

Does it vibrate with the clutch out in Neutral? Or only in gear?

If only when it's in gear with the clutch out it's sure to be something from the driveshaft back. Could have shifted or damaged a universal that only presents when under a torque load.

I don't know what it does in neutral but as soon as the pedal is pressed in it stops with the shifter in gear. I'll be looking from the driveshaft back I think.

A trip to a good alignment person might help...

Vibes with clutch in at speed? If so, could be driveshaft. Check crossmember mounts, etc. does it vibe at the known speed trans in neutral? Get as many clues as you can.

George
.

I don't know how people feel about the safety running the car while on a lift or stands, but I know people do it. That may be a good way to zero in on it.

I assume when you push the clutch in, coasting, you allow the engine RPM fall. Ever try pushing the clutch in, coasting, and keep the RPMs near where they were had the clutch been engaged? Wondering if it’s flywheel related somehow.

This.

It's "divide and conquer". Determine if it is engine speed related, stationary (clutch in and out) or vehicle speed related (even coasting with the engine off).

Once you eliminate half the equation as a possibility you can focus more earnestly on the remaining stuff.

K

We should start a separate thread about PEOPLE PULLING RIGHT OUT IN FRONT OF ME, or yesterday I had a guy completely cross the centerline in order to come at me head on.

Normally I can get away, but as luck would have it there was a disabled vehicle on the shoulder on my right.

I bet our mirrors touched as we went by.

K

Remove the driveshaft and get it balanced.

So glad you were able to save it! From the looks of the road, you were very lucky the ditches were not too deep. A very nice car with excellent color combo, can't say I have seen one like that before. Is there any vibrations when sitting still and revving engine? Could the harmonic balancer got damaged in the accident?