a vibration problem at 40 mph
 

i have a vibration at 40 mph that i just can't find the cause of.i have had severial motors put in and out of the car,rebuilt the transmition,rebuilt the front end,rebuilt the steering all the way through.all of this work has not done any good at solving the vibration problem.all that is left is to remove the rear end and start rebuilding from top to bottlem but before i do that i want to run it by you guys to get your opinion.there is no noise at all from the rear end.it all apears good except the rear axel keyseats are a bit lose but i keep the rear drums tight to prevent anymore wear.i just don't think the vibration is found there.i did put in a new universal jount when i overhauled the transmition however from that point back i have not touched anything.what is the runout spec.on the driveshaft if i decide to take it out and check it?

Re: a vibration problem at 40 mph
 

tires balanced?

Re: a vibration problem at 40 mph
 

On my 31 coupe I have a vib. at about 40 mph, if I stay at 38 or go a little over 40 it will smooth out, It also depends on the slope of the road, no vib. on a slight up hill grade, but the vib. comes back with a slight down hill grade. stright and level is ok, but I still have to stay below 40 or above 40.
Have you drove another "A" model to compare?...I think there is some vib. in all of them due to the 4 cly. motor of the 20's and 30', JMO

Re: a vibration problem at 40 mph
 

i have tryed too balance the tires.it seems to be coming fron the drivetrain and not the tires.

Re: a vibration problem at 40 mph
 

My 30 coupe is exactly the same...all new except the rear end

Re: a vibration problem at 40 mph
 

the "driveshaft " balance it .

Re: a vibration problem at 40 mph
 

if u can fell the vibration going front to back is the driveshaft ..

Re: a vibration problem at 40 mph
 

You could take off the speedometer "turtle" and look for movement and play in the front driveshaft bearing ---have you run the car with the wheels off the ground, perhaps on a lift and looked for the vibration

Re: a vibration problem at 40 mph
 

i am going to jack the rearend up tommorrow and get it up to 40 mph and see what i can find.i may also take the rear wheels off to eleminate that being the problem.so far i think it is the drive shaft but i would like too get more input from you guy,s.

Re: a vibration problem at 40 mph
 

Steamgas ..............
If you push in the clutch at 40 mph and it doesn't stop, it is, probably your tires or driveshaft componants.
MIKE :)

Re: a vibration problem at 40 mph
 

Do you have the bearing and race in the torque tube.

Re: a vibration problem at 40 mph
 

i just jacked up the rear end and ran the speed up to 50 mph and pushed in the clutch and tried too tell the differance between the drivetrian and the wheels.the wheels are out of round and do wobble a bit but the vibration is coming from the drivetrian.i know how too square up the flywheel housing(.005)and the flywheel(.003).all things point too the driveshaft.i may take the speedometer out tommorrow and look for endplay there before i take everything out from underneath it.

Re: a vibration problem at 40 mph
 

this is a 1929 truck.which bearing do you mean?the one at the transmisson or the one at the banjo housing?

Re: a vibration problem at 40 mph
 

I think George means the one inside the front of the torque tube !!
John Cochran

Re: a vibration problem at 40 mph
 

Most Model A's have a vibration at this speed. I lightened and balanced the flywheel many years ago and it helped but still has a bit between 42 and 45mph. I have driven many A's with the same vibration around this speed/rpm. Some are worse than others.
Good luck in your search.

Re: a vibration problem at 40 mph
 

Well, I'll be interested in how this turns out. I'll be amazed if it's the driveshaft--a straight solid rod that lives its life rotating not very fast about its long axis in a protective torque tube.

Is there a growely or rumbley noise, or any other "new" noise that occurs along with the vibration--like a bearing may be involved?

As others have said, some vibration around 40 is common; mine has a vibration point at 35 mph; If I pay close attention, I can detect it at the same rpm in 1st and 2nd gear--that's the motor.

In my experience, because of how everything is connected to everything else, it's very hard to be sure where a vibration is originating. Exactly what happens when you push in the clutch at 40 mph? I remember shearing an axle key and being absolutely certain that my transmission had exploded.

Steve

Re: a vibration problem at 40 mph
 

the vibration quits when i push the clutch in.there is no noise in the rearend.nothing scrubing,draging etc.mabe i just expect too much from it.i hear of people taking long raod trips in their car.how could the car or truck hold togather with a vibration at 40 mph.i would not take mine past the post office and even then i had better have the phone number to the wrecker crew with me.

Re: a vibration problem at 40 mph
 

As long as the wheels don't fall off go past the post office.!! Have Fun!!!

Re: a vibration problem at 40 mph
 

My coupe did the same thing until I replaced the clutch and flywheel with a balanced and lightend flywheel. Yes it stll vibrates but at higher speeds 50-55. I typicaly drive 45 max.

Re: a vibration problem at 40 mph
 

I assume this is while on the jack stands. You could take tire imbalance out of the equation (or put it in for sure) by doing the same test with the wheels removed.

If the vibration goes away above 40, I agree with the others about just driving it.

I'm still betting on the wheels/tires. Have you taken them to a shop that has the mounting adapters to spin balance them? Discount Tire did my new Firestones using stickon weights when I bought them thru them, however my prior set of Universals were ruled basically unbalanceable--the guy said he'd have to double stack the weights and even then couldn't do anything about their side-to-side issue.

Steve