Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks



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Joined: Dec 2006
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Shade Tree Mechanic
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Yes, I noticed a vibration at about 30-45 MPH when driving and I was wondering if it could be the clutch pack. I read that the "X" on the flywheel and the "X" on the pressure plate should be lined up as close as possible and I'm not sure that was done. If not, would that cause a bad vibration? Could I line them up without removing the transmission? I was thinking of just backing off the pressure plate bolts and spinnning it but I dont want to screw anything up. Dave


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The matching of the X was not mentioned till the later type clutch was used (1938)...and this was only if the original pressure plate was removed and then reinstalled.The new replacement pressure plate would not have the X.
I doubt if a little unbalance could be detected in a 1936 due to the heavy flywheel used, however rotating the pressure plate on the flywheel could be attempted.It may be a one time rebuilt unit out of balance.
You could also have pistons or connecting rods of unequal weight.When the 1936 engine was assembled at the factory they choose pistons and rods that has equal matching weight.This was their idea of balancing an engine.Then years later one or two of those parts were changed and the balance was really off, but it seldom produced a noticeable vibration.
Will the engine vibrate when the car is not moving and you bring the revs up?Or is the viabration there only when at that speed on the road?'''if so it could be the U joint or the drive shaft bushings (inside the torque tube) which is common.
An experiment to try if it is an engine inbalance problem would be to place a weight under a pressure plate to flywheel bolt -move it to different locations, and see if it helps.I would try using a wheel weight of about 2 ounces.Perhaps the rim attaching part could be modified to fit behind the bolt head.


Gene Schneider
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Thanks Gene. The vibration is felt when the engine is running and the revs brought up.... Also, the 1936 Manual mentions the "X" lining up... I'm going to try it and let you know.


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Is it possible that one cylinder is not firing? Use a screwdriver to short out each cylinder one at a time and see if you notice any difference in cylinders.

You may also have "crossed wires".

When did the problem appear?

Agrin devil


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Thank you, NO its runs great with no miss. I just got this car on the road with a new engine. Seems to be vibrating hum at 30-45 MPH I did not take it over that. I will check motor mounts just I installed new.


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If you do try rotating the pressure plate, if you can secure the clutch parts (pressure and clutch plates) away from the flywheel try starting the engine and check for vibration then. no vibration is pressure plate unbalanced if it still vibrates either flywheel or engine imbalance.
Providing you undo the pressure plate bolts evenly (no more than a turn each at a time) you should do no damage and tighten the same way. Should ALWAYS do pressure plate bolts this way.
I have found flywheel imbalance whith a couple of your buik V6 3800 over here.
Tony

Last edited by tonyw; 04/01/07 05:51 AM.

1938 1/2 ton Hope to drive it before I retire
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Just wanted to let you all know that I was able to line up the
"X" without removing the transmission. I had to loosen the clutch fork and than the 9 mounting bolts and spin the pressure plate untill I saw the "X" thu the bolt hole. Put everything back together and the vibration is for the most part gone.... There is still a little but nothing like before.

Dave


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Dave
Good to hear you have basically fixed your problem without major pull down.
Tony


1938 1/2 ton Hope to drive it before I retire

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