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Doubleclutch 05-14-2012 12:04 PM

Drivshaft Length and Balance?
Hi Guys

I have a 70 Buick with a built 455 that has a 65-70 MPH and up :confused: vibration. I have gone around and around with the tire balance guy and he says after a couple of sessions to look for something else. Under the car I have two problems with the driveshaft. This is a conversion from a 350 to a 455 with a TH 400.

First is there seems to be an excessive amount if sleeve showing at the tailshaft. I have 2 inches showing with weight on the wheels. I searched the site and it shows 1 1/2 is recommended. I assume the extra 1/2 is OK with my HP around 350 since its holding but looks excessive.

Second is the driveshaft has been sectioned/cut at the rear yoke. The welding looks very amaturish at the join. I'm going to try to spin it and see if its true. Assuming its true, can there be a balance problem enough to shake a CD out of track at 70?

Thanks as always Chuck 05-14-2012 12:35 PM

Amateurish welds on the driveshaft aren't good. Since it looks like an amateur job, have you checked the phasing of the U-joints? Are they set up in the same plane?

MARTINSR 05-14-2012 01:53 PM


Originally Posted by Doubleclutch
Assuming its true, can there be a balance problem enough to shake a CD out of track at 70?

Thanks as always Chuck

In a word YES! Just the weld it's self (weight) I imagine can set it off, the weights I have had installed ballancing shafts I have modified were not very big.

This doesn't sound very good at all.


prostreet6t9 05-14-2012 06:32 PM

Remove the Shaft and check it for the correct length. Any "sectioned/cutting" is a bad deal and is a good idea to fix. Take it to a Driveline shop and get it Retubed "longer if needed".

Doubleclutch 05-17-2012 10:06 AM

Thanks Guys
I'm getting the same advice locally here. The 2 inches is excessive so I need about 1/2 added. Also the retube and balance is relatively inexpensive--its the u-joint yokes that add up.

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