C2 Engine Vibration while accelerating from 55mph

[Joseph A.]

Experiencing engine vibration (or could be drive train), when accelerating from 50-55mph. Not feeling it in the steering wheel, but on accel pedal and underneath driver seat. Vibration stops when returning to 50 mph. No vibration at lower speeds while working through gears.
Car has new "balanced" radial tires.

Any thoughts

[Patrick H.]

Re: C2 Engine Vibration while accelerating from 55mph

When did it start?
What changed, if anything, right before it started?
Any recent work done to the car?
Etc

[Joseph A.]

Re: C2 Engine Vibration while accelerating from 55mph

Just started this week. I've had the car 2 months. No work on the car except I fixed a fuel leak on the Holley 4bl front bowl.

When did it start?
What changed, if anything, right before it started?
Any recent work done to the car?
Etc

[Leif A.]

Re: C2 Engine Vibration while accelerating from 55mph

Experiencing engine vibration (or could be drive train), when accelerating from 50-55mph. Not feeling it in the steering wheel, but on accel pedal and underneath driver seat. Vibration stops when returning to 50 mph. No vibration at lower speeds while working through gears.
Car has new "balanced" radial tires.

Any thoughts

Are they "correctly" balanced?? Did this problem exist before the new tires were installed?

[David H.]

Re: C2 Engine Vibration while accelerating from 55mph

Joseph

Are they "correctly" balanced?? Did this problem exist before the new tires were installed?

What he said.


From a quick search of The Google:

around 55-65 mph




Typically, vibrations felt at highway speeds are a good indicator of an out-of-balance tire. If the vibrations occur at highway speeds within a range, usually around 55-65 mph, and dissipate by either slowing down or speeding up, then it is best to assume that your tires are out of balance.

Dave

[Richard M.]

Re: C2 Engine Vibration while accelerating from 55mph

Agree/Agree....

Have them rebalanced on a Hunter Road Force balancer.

"Road force balancing is a more sophisticated technique that can find imbalances that standard balancing cannot and can remedy them. This technique makes use of a device that exerts a controlled force against the rotating tire and wheel assembly."

Rich

[Mark E.]

Re: C2 Engine Vibration while accelerating from 55mph

Agree. Agree.

Also check all u-joints. They can cause this symptom too.

[Duke W.]

Re: C2 Engine Vibration while accelerating from 55mph

Does it only occur when you are accelerating in the 50-55 mile range, or does it exhibit when traveling at constant speed within that range? Also does it occur in all gears, and can you feel it at over 55 MPH while at steady speed or accelerating. Test to as high a speed as you can safely do in your area?

This will help establish whether the vibration is engine speed sensitive. drivetrain speed sensitive, or engine torque sensitive.

Out of static balance or out of round tires cause "steering wheel shake". Some radial tires can have enough difference in spring rate around the circumference of the tire to cause a vibration, which the Hunter 9700 can detect in addition to out of round.

but since you said you can't feel the vibration in the steering wheel, I suspect it is not wheel balance, however, how long after the new tires were installed did you notice it?

Duke

[Bill B.]

Re: C2 Engine Vibration while accelerating from 55mph

Joe, as Mark indicated, driveshaft u-joints might play a role in your issue. I bought my '70 back in 1977 that had previously been involved in an accident. There was an annoying vibration felt in my shifter above 60 MPH. Turned out to be misalignment (angle) of the transmission output to differential yoke. Was wondering why my driveshaft u-joints didn't last very long!

[Joseph A.]

Re: C2 Engine Vibration while accelerating from 55mph

All - Discovered (3) wheel bearings were in need of repacking. Plus replaced U-joint.
Vibration gone. Thanks for all the input. - Joe

[Bill M.]

Re: C2 Engine Vibration while accelerating from 55mph

I had the same problem with my 69 427 Coupe...4 speed.

Old motor head told me just to drive it as the tires may have some soft spots from sitting. I then realized that it had sat for many months in storage. I did some nice rural 35-55 mph areas on the weekends and it went away. My vibration was very bad at 55mph.
Just my thoughts

[Leif A.]

Re: C2 Engine Vibration while accelerating from 55mph

All - Discovered (3) wheel bearings were in need of repacking. Plus replaced U-joint.
Vibration gone. Thanks for all the input. - Joe

Joe,
You did re-pack all four wheel bearings, correct (I'm assuming front bearings)?? Which single U-joint needed replacing?

[Edward J.]

Re: C2 Engine Vibration while accelerating from 55mph

Joseph, road test car and note the RPM when noise starts, then when your home slowly increase the RPM in neutral or park (auto)to see if you can duplicate the noise. If your lucky you might locate, you will need a extra hand while you crawl under car to locate.if car noise a rolling issue can be tough to locate.

[Joseph A.]

Re: C2 Engine Vibration while accelerating from 55mph

Repacked all four bearings and replaced all u-joints all around.
I figured I'd have all replaced while up on the lift and didn't want to "guess" which was bad.