drive shaft balance?

For a race only application, Is there a minimum speed at which the driveshaft should be balanced? Would it be crankshaft rpm at the stripe? I know that a lot of shops can't balance at a "high" speed, but what speed is high enough?

I run a driveline shop in Amarillo. Our machine runs them at about 600 rpm. as long as it is balanced as close as possible,( less than .03 oz) on each end and with less than .005 runout, you should be fine.

We have built lots of drive shafts for sub-9 second cars without complaint.

You should always balance a driveshaft at speed. Many will be fine if balanced at 600 rpm but some won't. Most importantly you MUST know what the critical frequency of the shaft is compared to your actual driveshaft speed. 15% difference (critical speed higher than actual driveshaft rpm) is a safe target.

There is a reason I have a 4" mild steel shaft balanced at 7500 rpm in my race car. Smooth as silk.

Just went through chasing the final vibration in my Dart and it was the shaft and was out of round .008-.010 iirc and was a mess above 5000 r's. Even though my 1350's were still good, he put new ones in and balanced it above 3000r's iirc and it's smoother than ever...........

What driveshaft companies in Ohio do high speed balancing. I've had mine balanced 3 times by a shop in Cleveland. Each time it is a bit better but still not good enough for my tastes.

"balanced it above 3000r's "
Is this the critical number? Like most people, I'm on a budget. But I would prefer to do this only once.

Several people I race with used Custom Clutch in Canton Oh for their driveshafts.

Custom Clutch, Joint & Hydraulics, Inc.
3417 St. Clair Avenue
Cleveland, Ohio 44114
216-431-1630 office 216-431-6048 fax 800-654-0428 toll free
My friends used the Canton location 330-455-1202. No complaints.

I got mine from Mark Williams.

The critical speed is where it will vibrate and is also known as the resonant point. You don't want to turn your driveshaft above the critical speed (again - stay 15% below it for safety margin).

This really only become a problem for race cars that turn some rpm. But check out Mark Williams site or call them.

http://www.markwilliams.com/driveshafttech.aspx