Thread: vibration

Tweet

Hi guys,
I need some help. Have a '68 Camaro SS w/ a BBC 396 and TH350 trans. The car has a vibration (extremely noticeable) between 60 and 67 or 68 MPH. The wheels are fully balanced, the U-joints are brand new, etc. I have two areas that I haven't attended to....first, the left header is slightly touching the steering box....and second, I had the drive shaft constructed from a heavy-duty Impala one.....but I never had it balanced. I've also been informed about brake drum balancing (car has 4-wheel drum)???? I'm struggling w/ this. Any assistance would be greatly appreciated. Thanks!

was the driveshaft cut and not balanced? Did you put undercoating on the driveshaft? Undercoating on the driveshaft will cause it to be unbalanced. Balancing a drive shaft is extremely important.

if it were brakes I would assume that it would be a problem that covered a broader speed range. Perhaps wheel hop from bad/blown shocks?

Thanks for the info. The driveshaft WAS cut and welded, but never balanced. There's no undercoating on it, but I think I'll explore balancing it. Thanks again, Brian

yes, definately balance it, even just changing the u-joints will change the balance sometimes. Plus most places charge well under $50 to do the balancing. A very smart investment in my opinion.

Did a shop cut and weld the D/S or someone else?? If they put the U jiont hubs out of line it will viberate VERY BAD.

It was cut and welded by a reputable shop....just never balanced. Question now is....how does one balance a drive shaft? Never done it....or seen it done. Just a question. thanks

Take it to a machine shop that builds drive lines, they will spin it up an apply weights to bring it into balance. Not every machine shop does this, make sure you ask so they are not just farming it off to some place else. That way you are dealing with the people who actually do the work. My local shop charged about $150 to clean, cut, weld, balance, install new joints and repaint mine. So balancing should not be more than 1/2 labor.

Pat

Just paid $145.00 for new drive shaft to be made and balanced chevy front ford rear new U joints all I supplied was the rear flange. I had one done on my wifes suburban last year right there in Kal. don't remember the name of the shop. Think that was $130 but only needed the front half.

Make sure the driveshaft is running true before you have it balanced.
They don't always need to be balanced, but when they do....

Check your tires for out of roundness as well.
Usually not a problem with todays tires, but it happens now and then.
Might check wheel runout as well.

All of this checking can be done with a screwdriver balanced or taped onto a jack stand, turning the item to be checked by hand and seeing if it runs true or not.

As far as your header touching the steering box, not good.
For the heat problem at the box among other things, but that contact will magnify any vibration coming from the engine.
Note the rpm at the unbalance point.
Stop the car, put it in neutral, spin the engine up to that rpm and see if the vibration comes in.

Another one you can do is get up to the speed where the vibration comes in and slip the trans into neutral and coast for a little bit.
That will tell you if the problem is in the engine or drivetrain/wheels/tires combo.

Do a little investigation before you drag your wallet out....

i agree check out other avenues before looking at the driveshaft balance i had my shaft shortended about 16 inches , the machine shop i had it at told me they never balance them and that he removes the balance weights.
when i asked why no balance he advised most shafts are not welded straight to start with causing the inbalace. he advised he puts the shaft in the lathe and makes shure it dead straight befor welding and them spins them again to see if any problems.
mine was perfect without anything. eyeball the sahft to see if sone straight and that the ends are phased correctly.
i also think the brake drum balancing is hooey

i've cut and welded 15 to 20 shafts over the yrs. and never had the need to bal. one. i'd spend that 125.000 somewhere else. i'd make sure the shaft is straight first, then check the tires close.

I experienced the same type of vibration and was able to pin point the problem to the flex plate. It seams that some flex plates have a weight for balance on some 5.7 and 4.3's. Ive never had a drive shaft balanced as long as the ends were phased.

Phasing and balancing is VERY important. Sounds like your on the right road.

You've gotten some sound advice above.

I noticed you have drum brakes all around? My first car was a '67 Camaro with a sixer in it, drum brakes, and it did not brake worth a darn, particularly when it was wet outside. Are you comfy with the brakes on yours?

Regards, Kitz

Originally Posted by m falconstien

I experienced the same type of vibration and was able to pin point the problem to the flex plate. It seams that some flex plates have a weight for balance on some 5.7 and 4.3's. Ive never had a drive shaft balanced as long as the ends were phased.

i agree with the drive shaft statement, but not the flex plate. if it was the flex plate then it should do it sitting still also.