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Joe D

I have an "intermittant" (aren't they the worst?) vibration problem in my 1966 roadster. The most intermittant vibration occurrs at higher speeds, aproximately above 50 mph. It feels like a high frequency or shuttering in the floor area because I can feel it in my feet. I have balanced and changed the tires three times (new radials), installed a fiberglass leaf spring, sensa-trac gas shocks, ball joints, trailing arm bushings, wheel bearings, etc.
Everything seems tight and as it should be. I even had the drive shaft balanced.

The second vibration is more consistant with hard acceleration. The car seems to shake from side to side more with more acceleration.

None of these are in any way severe but seem to be more of a nusance than anything else. The car is top-notch (NCRS Top Flight) otherwise. Any other suggestions?

Thanks for the suggestion about the wheel bearings but they have all been replaced. Everything underneath seems tight.
It might be drive shaft

Did you mark drive shaft position to rear end before you removed drive shaft? If not get shaft loose from rear and turn shaft 180 degrees and attach it again. This helped my previous ´64 Coupe.



No, I did not mark the position of the drive shaft, only front and rear.

I'll unbolt the shaft and rotate it 180 degrees. Did your 64 Coupe experience the same symptoms as I described?

Thanks for the advice

Joe D
Motor mounts?? clutch??

If you have a weak or broken motor mount, then under aceleration the engine will try to "lay over" and will drastically change alignment. Using a large screwdriver or prybar, try and move the motor mounts. With time, oil and grease ruin the rubber........even on NCRS cars. Replace as necessary.

If that all seams well, remove the dust cover from the rear of the flywheel and get a good light and do a clutch inspection. Look for lose parts or bolts lying in the dust shield. Using a flywheel tool, rotate the engine so you can inspect as much as you can see.

Last month I helped a friend diagnoise a similar vibration problem, and we finally removed the trans and looked at the clutch. All the parts present were working, but we found whoever installed the flywheel stripped a bolt, and put in another non matching "Dorman" special from the junk drawer and used a plug to hold it. We removed flywheel, found another correct replacment with no butcher holes, had it surfaced and "BALANCED" , and reinstalled the clutch assembly and trans. Car now pulls 6500 RPM with no vibration in three gears.......and we ran out of freeway in 4th.
Good luck,

Thanks for the suggestions about the motor mounts and the flywheel. It makes sense from both types of vibration that it is more likely a flywheel, although a deteriorated motor mount could contribute.

Unfortunately, the flywheel is a bigger job so I'll check the motor mounts first.

Thanks again for the advise,

Yes. Same symptons


I did have same symptons with my ´64. Best in this 180 degree rotate is that it is so easy to do and test. In my car it helped.


The other way to check motor mounts

Put the car in the driveway, chock the wheels BOTH ways, apply the emergency brake ( if it works )

Hood up

If the car is an automatic this is a piece of cake...if its a stick dont do the test to long.

Put the car in reverse and start to accelerate slowly.... ( if it's a stick start releasing the clutch ) the enging should lift a BIT and stop, if it keeps raising... that side motor mount is shot.

Repeat the test in Drive ( or 1st ) and observe.

That's the way I learned.

Try the driveshaft thing... if nothing else it will
point you in the right direction

I had a vibration in my 65 coupe. 327 4sp. It was the pilot bushing. You can check for that by removing the inspection plate and having someone (I used a board) hold the clutch to the floor and see if you can move the clutch disc. If you can move it, the bushing is worn and the vibration can only be cured by replacing the bushing. A lot of work for a part costing a couple of bucks. Good luck.

Good point - every time I do a clutch replacement on any of my cars, I pull the old bronze pilot bushing and replace it with the GM needle roller-bearing part ($13.00); they don't wear, and last forever. Your dealer can get it for you, or any speed shop has them re-packaged by Moroso, etc.
Dittos on the needle bearing pilot. Any time you have the trans out you should replace the bronze bushing with this bearing if you haven't already.

Another thought - the rubber "donuts" between the diff front mounting bracket and the frame crossmember deteriorate over time, and when they get bad enough, they telegraph diff noise and vibration into the frame; they will also cause a prop shaft vibration due to the resulting change in rear pinion angle, especially under acceleration, and can actually cause the rear of the prop shaft to rub on the floor pan.
Save me the trouble

I have the same exact problem in my 65. Its about to rattle the shifter to pieces. At least I have somewhere to start.

Thanks to all who contributed their ideas and knowledge in helping to solve the vibration problem I described. Believe it or not, the culpret was the engine timing.

I advanced the timing from about 6 degrees advanced (where the book says it should be) to about 10 degrees advanced. Then, I retarded it about one degree (to keep it from "bumping" the starter) and the engine absoultely roars with no vibration at all through the speed ranges. I had to tweak the dwell angle a little to smooth the idle but now it runs great.

Again, thanks to all who took the time to offer their suggestions!

Joe D
Shifter rattle


Solid Axles and Midyears are famous for rattling shifters. Of course a vibrating driveline/engine exagerates the problem. Check with Paragon Reproductions www.paragon-corvette.com . They have a shifter rebuild kit with new shims ect. that will greatly reduce shifter rattle.

I Love it when the cure is so easy !!!

Great to hear that all that was needed was a good tune. Check your distributor advance curve. Make sure the vacumn advance is up to par. Check the book for total advance for your motor. Most Corvettes run great with 36 to 38 degrees total advance.
Good luck
You probably already checked this but how is the tail shaft bushing. If you have more then a little play it can run out and cause the type of vibration you are describing.

I had the one go bad in my autocross vett so bad that it would jump out of gear when running high speed events.
corvette vibration

Did you ever correct the vibartion you had in the Vette? I have what I think is a similar condition?
bad vibes

One of my 67's had similar vibrations. First between 50 and 60 and a different one between 75 and 90.:crazy

The first was cured by rotating the driveshaft, the second was more elusive. The solution finally presented itself one night while passing through West Virginia.

First I thought a rock got thrown up by the left rear tire. Then rounding a curve at illegal speed, a subtle change in road feel. I stopped in Charleston, Jacked the car up and got the answer- loud grinding on outer left side. I feared the worst. I had visions of a trailing arm rebuild. Turned out to be the outer u joint.
After replacement the second high speed vibration was gone.

The ujoint showed no sign of failure; no play whatsoever, but was dry inside and a few of the needle bearings were out of round.

Administrative note

Take a few minutes to look at Nick's web site. He has some beautiful cars. I especially enjoyed the last picture of your hill climber with the Purple People Eater and the 1966 Penske L88 prototype.


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