Car Shakes

[Rockbass]

Hi Everyone,
Car is 1947 ford flathead tudor new to me. Car shakes above 55 mph and decrease only slightly at 70 mph. Had all 4 tires balanced, no change. Steering wheel does not shake. Front end feels nice and tight. What do I check next? Thanks in advance for your input.

[RalphM]

Not as simple as my answer, but check everything. King pins to steering box, any amount of wear above specs can cause it. And I’ll probably take flack for this, but
If all else fails, install a stabilizer.

[51 MERC-CT]

With the car in neutral and out of gear, rev the engine to the appox speed where shaking occurs to see if its in the flywheel, clutch and associated parts.
Jack the rear wheels off the ground and run thru the gears to check drive line and associated parts. (jack stands recommended)

[chap52]

Jack up front end and give the wheels a good back and forth, top/bottom, front/back and determine if there is any play. I know you said that it is tight, but check again.
In the Southwest if we leave a car parked on a slope or in the hot sun sometimes it takes awhile for the tires to return to round. Works just the same in cold country. Especially if tires are old and dry.
Do as suggested and check pitman arm and all front end components with the car front end off the ground.
OK, I'll join RalphM on the hit list. A stabilizer is a band aid but it is good until your ready to dig into the front end.
Enjoy the adventure, Chap

[50fordcoupeman]

For whats it worth, I had a similar once but with a little different symptoms. It ended up being a broken motor mount. Good luck!!

[hook00pad]

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It could easily be a bad tire. They will balance out even if they are not round. How old are your tires?

Al Hook

[19Fordy]

What happens when you move the rear tires to the front?
Are your backing plate bolts tight?
Check all the bolts and nuts related to your front suspension including the condition of the rubber insulator inside you front wish bone ball cap at the X member.

[JSeery]

Also, how were the tires balanced? Need to be checked on the car if they continue to be an issue, but it is sometimes difficult to find someone with the equipment to do it. There can be lots of tire issues, what make of tire are they?

[deuce_roadster]

Tires can balance on a slightly bent rim. Make sure none are bent. Also it is a long shot but a bad wheel bearing could do this with perfectly balanced tires.
I would double check every thing that turns or pivots in the suspension, including the shackles.

[Shu47]

I think the key point the OP made was the steering wheel does not shake. From my experience, normally a front end problem will be transmitted to the steering wheel. I think that 55 MERC-CT and 50fordcoupeman have the right ideas.

[FlatheadTed]

Greasing the front U joint of the drive shaft is another option ,I had a vibration on my 35 and this helped .Takes a pint ,this can also help the front Torque Tube roller bearing ,they have been known to seize from lack of lube,

[adileo]

Originally Posted by hook00pad

It could easily be a bad tire. They will balance out even if they are not round. How old are your tires?

Al Hook

Agree this was the case with my 39. Replaced tires and smooth at all speeds.

[19Fordy]

As a last resort, check the bolts that secure the steering box to the frame.

[alanwoodieman]

2 second flathead ted, had a 36 do the same thing. but I would check the rear tires for bad cords--ie tire coming apart!

[Rockbass]

Thanks everyone for your replies. The tires are at least half worn so I am going to recheck them.

[JSeery]

I don't remember what it's called, but there is a tire/wheel test where they apply pressure to the tire will it's spinning.

[RobR'35]

"Road force" is what I believe the test is your thinking of.

[JSeery]

Originally Posted by RobR'35

"Road force" is what I believe the test is your thinking of.

Yes, believe that is it. I have never used it, but there are a lot of reports of it identifying issues.