Strong vibration at 60 mph but stops when I press in clutch

P

Pete W

Well-known member
Hi,

I have amanual tranny 1961 Comet with a 144. When I get to about 55/60 MPH there is a strong vibration and it keeps getting worse the faster I go. When I press in the clutch it's as smooth as silk. A friend said that it is the engine. He said if it is the tranny, driveshaft, etc pressing in the clutch would not stop the vibration because everything would still be spinning.

Any ideas would be greatly appreciated. I really need to fix this.

Thanks,

Pete
 
I just read your post again. It IS something from the clutch back, not the motor. When you step on the clutch, it disengages the drive-train and all goes smooth. I bet it's just your u joints, check 'em out. Easy to swap and cost about $10 anywhere.
Post back with your findings.
 
When I step on the clutch isn't the drive shaft and tranny still engaged because the rear wheel is spinning?

I'm thinking somethings up with the engine under load. In nuetral it runs smooth. When I accelerate under load it gets worse.
 
I need to double check that but as far as I can remember it only totally stops when I press in the clutch. It does get MUCH louder when I put on the gas though.
 
Hard to say. When you clutch in, the input shaft stops rotating, so that is another possible source of distress.
 
I changed them out and had the drive shaft balanced about six months ago. Could they have gone bad? I was thinking about getting it rebalanced
 
It did it when I first bought the car. I rebuilt the tranny, new U joints, new clutch, and had the drive shaft balanced and it went away. Six months later(now) it has started up again. When I get to 55 mph I hear a growling noise and the vibration starts, especialy during acceleration. It gets worse as the speed increases.

I read that a fellow unbolted the rear U joint and turned it 180 degrees and his vibration went away. It sure would be nice if that cured it!
 
I would double check those ujoints. My son had a similar problem and it turned out that the guy who previously had the car had replaced them but did not tightened the nuts properly and they loosened up.
 
i think if it was somthing with the clutch it would be happening when he hit the same RPM range in every gear not just the higher gears
 
Sounds like a bad spark plug, or wire or carbon trail in the distributor. All the plugs fire ok under no or light loads.. Under a load the voltage requirement increases as the load on the engine increases until the spark escapes somewhere rather than firing the plug. This causes a miss which causes the engine to shake. It feels like a vibration. Check all the plugs, discard any which have oil or carbon on the insulator. Check the plug wires with an ohmmeter. Sometimes the carbon fiber will break down which causes an arcing inside the insulation usually on the spark plug end. The sparking burns the carbon fiber creating an increasingly large gap and can cause a misfire under a load. One of the terminals inside the distributor cap can have a carbon track leading to ground. If there it will be visable. Sometimes this can happen on the outside of the cap also. Good luck. Post your findings when you get this cured.
 
I want to thank all of you for helping me out. First I'll work on the ignition system. With the exception of the plugs nothing has been replaced. I'll replace the plugs again, the distibuter cap, points, rotor button, condenser, and plug wires and see if that solves the problem. If that doesn't work I'll look at the drivetrain. I hope it's not that because with the exception of the rear end, I've replaced or balanced everything.

Thanks again,

Pete
 
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