Packard Forum Index » Pre-War (1899-1942)

I have been working down my list of things to do on my 1938 super 8. Got all the major service done , brakes adjusted, tuneup including new autolite plugs, points, condenser, pulled distributor which was binding with all the old grease, pulled the ee23 machined the warped body, honed the accelerator pump bore, front end although not perfect pretty close. The next item is a engine vibration that appears at 20 mph and then becomes unnoticeable at 50. I can feel it in the power band also in second gear. The engine idles smooth and quiet, starts easy however the clutch although does not seem worn it has a bit of jerking action if engine is above idle and you release it.
The car came with a list of items done to it with a dollar value of what was spent, but no receipts. It showed thousands of dollars spent on engine bearings, Pistons ,crank grinding, sleeves, flywheel and clutch . Well over thirty grand . Of course I know money spent does not mean it was done right! Naturally I do not want to take apart a engine that burns no oil, leaks no water, has no blow by and is so damn pretty with engine paint and senior jewelery. So here I could use some opinions. My thoughts were that if it was ignition or carb the vibration would sometimes very and this never changes. I thought maybe when they did the clutch job they lost the balance by rebooting clutch in a different place? The front balancer comes to mind. Is there a test for them and what are the options for repairing? I hear that one place in ca. Takes out the discs and pours in rubber? Thank you all in advance for any suggestions,

Probably tire"/wheel out of balance. Altho in most caes it starts at 40 mph and goes awY at 50.

At 60 mph I can put in neutral and coast down and feel no vibrations

A "list of things done...stated dollar value... but no actual receipts"....?

Not good ! Inability to confirm which shop did what, means all I can do is give you some wild guesses!

I would not focus on an engine out-of-balance - such as mis-matched pistons, con-rods, goofing up the crankshaft "counter-weights", flywheel - clutch disc, etc. ANy balance issue in those areas gets worse with rpm. You'd know it - pretty durn obvious.

I'd start with the drive shaft & U joints. Fortunately, your car used front & rear U-joints in a size that is avail. brand new today. A "harmonic" caused by a slightly bent, out-of-round, out of balance drive shaft would be a good place to start.

Remove that from the equation first - then we can discuss more esoteric (and expensive ! ) ideas...!

There is a simple way to determine if it is an engine or a chassis problem. In neutral with the brake on rev up the engine and see if you get the vibration at speeds that would make the car go 20,30, 40, 50 etc. If no vibration then it's a chassis issue.

If a chassis issue put the rear axle on jack stands and block the front wheels fore and aft. Start the car , put in 3rd gear and accelerate and see if vibration, if so it's most likely drive shaft related, if not then all that's left if tire balance or loose wheel bolts

IF the drive shaft is a 2 piece drive shaft (splined section of drive shaft thaat slides into opposite section of drive shaft) then make sure that the U-Joints are PARRALLEL to each other.

Can u feel any significant shaking or vibration directly at the steering wheel??? Or is it mostly vibration at your butt thru the seat???

All drive shafts that year are one piece

Thank you all for ideas, I started the car this afternoon and you could balance the coin so to speak at 500 to 1,000 rpm then the engine gets a mild shake which continues to increase with rpm. On the freeway at 50 and above I do not notice it, but without load in my garage I do not see it smoothing out at high idle and I am a bit afraid of Speeding up the motor that high.

Make sure that no two CONSECUTIVE firing plug wires are touching each other.

Unless they run thru a METAL tube then it doesn't matter.