steady vibration when reaching 30 mph in a 1936 Dodge d2 sedan

[Cratchet]

the motor is fairly fresh. I've checked the timing etc. i took the car with my brother at around 30 mph there was this steady vibration. i'm thinking possibly the drive shaft. any suggestions. also are these cars noted for vapor lock when driving in hot temperatures.

[hchris]

Yes and Yes

Edited October 6, 2015 by hchris (see edit history)

[Spinneyhill]

More information.... how long has it had this vibration? What did you do to it before the vibration started?

 

Could drive shaft be bent? Have you done anything to the universals etc. that might put something out of balance?

 

What about (new) tyre(s) or tubes? Balance weight fallen off?

 

If it were in the engine it would occur while standing at certain revs.

[Larry Schramm]

Maybe out of balance tire or an out of true wheel with excessive run out?

 

How old are the tires and might they have a flat spot?

Edited October 6, 2015 by Larry Schramm (see edit history)

[JACK M]

Try pushing in the clutch to eliminate engine and or clutch vibration.

A bad tire as mentioned may be felt more in the steering wheel. (swapping fronts to backs may tell you something).

A driveline has its own feel if you will, steady and varies with speed.

 

Bottom line is that there are different types of vibrations and the process of elimination may help you localize it.

[Guest Rp1967]

A reed tach is very useful when hunting vibrations if you can get your hands on one.

Set it on the dash and drive 30 mph , the reed tach will tell you what frequency the vibration is and then you will just have to deduce what part is spinning that speed.

[Cratchet]

Thanks everyone for your input. I haven't had the opportunity to solve the issue. I'm going to give it a go today and get back to you as soon as I find out.

[Rusty_OToole]

All cars today are more prone to vapor lock (unless they have fuel injection) because of the way the fuel is made.

 

Your car should have a simple tin deflector over the fuel pump. Route the fuel lines the same way the factory did and keep them away from the exhaust manifold and you should be ok.

 

Vibration, could be lots of things. You can throw out the clutch let the engine idle down and see what happens. This will tell you if it is engine or chassis. If it gets worse and worse as you speed up it is likely drive line. If it gets way worse at a certain speed then diminishes at higher or lower speed most likely a tire out of balance or a bent wheel.

 

Put it on a hoist and check the universals for wear. Check the wheel bolts are tight, wheels are true and there are no rocks or gobs of mud stuck in the wheel. Have the tires balanced. Check the wheels and have them trued if necessary.

 

If the vibration is bad at only 30 MPH I would suspect something is way off. Something obvious like a loose or bent wheel.

[Rusty_OToole]

There has been a lot of discussion on the vapor lock question. For old cars with low compression like yours, you can add 10% kerosene, stove oil or diesel fuel to the gas and this will help in most cases. But be sure your fuel pump carb and fuel lines are in good condition.

[keiser31]

You can see a curved heat shield above the fuel pump and under the exhaust manifold on this photo. The 1936 item is similar.

[oldcar]

Vapor lock must be something unique in American cars, in over 60 years of driving in more than 100 different cars of all ages from the late teens (1918) to the present (2015) I have never been troubled by it even in tempreatures of up to 40 degrees Centigrade. Re the Vibration issue, is it present if you bring the engine up to and hold it steady at about the same rpm as at 30mph while stationary in neutral. If ok this should rule out the engine. Now try driving at 30mph then depress the clutch. Does the vibration go or stay, if it stays is it better or worse. Having had the engine out are you sure you hooked up the tailshaft in the same location and are all the nuts and bolts fully tight. It helps if you mark the two flanges either with paint or better with a centre punch BEFORE you dismantle. Jack the front of the car up and see if the front wheels tend to turn back to the same position when you rotate them. If out of balance the heaviest part of the wheel will always go to the bottom. With the car still on the jack try the wheels for any looseness in the wheel bearings. 

If the vibration is present in the engine you may have to check that the flywheel is tight and that you replaced it in the same position on the crankshaft again It is a good idea to mark the location before dismantling.

Welcome to the joys of antique machinery.

 

oldcar.

Edited October 22, 2015 by oldcar (see edit history)