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122Dave 08-19-2006 04:29 PM

Vibration problem
Hi I'm new to this forum but I'm thinking you guys will have some good ideas to help me figure out my vibration problem. A little background info...I have '63 Buick 215 V8 hooked up to a Borg Warner t35 automatic. This combo is in my '68 Volvo 122. Every thing has worked out pretty well with the swap except I get a oscillating vibration which becomes noticeable about 3000 rpm. I don't think it is in the drive-shaft or rear because it gets worse as rpm gets higher in 2nd then goes away when shifting to 3rd. It then comes back as rpms build up. I had the harmonic balancer rebalanced so it is good. I am now thinking the flex-plate or torque converter might be out of balance. I took off the inspection cover on the bell housing and can see where the ring gear bolts the flex-plate. There are what look like extra bolt holes for balancing. Two of the holes had small bolts with different thickness heads. They looked like balance weights. Is balancing the flex-plate the problem and if so how can I balance it while it is still in the car?

xntrik 08-20-2006 08:11 AM

I would think that if the engine/transmission assembly are original then the balance would be OK. It does sound like a converter/flexplate problem.
As far as I know, unless there is a standard balance converter/flexplate available, custom balancing will require engine disassembly.

122Dave 08-20-2006 03:31 PM

Thanks for the reply. I am going to try to balance the thing in the car by adding weights and moving the weight around the the perimeter of the flex-plate. This seems a little hit or miss but if it works it will be better than taking the tranny out. If the trans has to come out I have a 4.6l engine I'll build and put in.

122Dave 08-20-2006 03:35 PM

Oh yeah, if you want to see the project go to

lamothe1 08-31-2006 01:48 PM

If you rev the engine to 3000 rpms with the car sitting still and in gear with the clutch depressed and it vibrates the vibs are coming from the motor, if it's smooth then I'd say the touble is in the trannie

njbloodline666 08-31-2006 05:21 PM


Originally Posted by lamothe1
If you rev the engine to 3000 rpms with the car sitting still and in gear with the clutch depressed and it vibrates the vibs are coming from the motor, if it's smooth then I'd say the touble is in the trannie

its an auto

lamothe1 09-05-2006 01:13 PM

Ops, I should have read your thred a little slower, but the same principle applies. Rev the engine to 3000 rpms with the car sitting still and in nutural and if it vibrates the vibs are coming from the motor.

cucumber1949 09-05-2006 01:41 PM

If bringing the revs up to the range where it vibrates while sitting still in neutral, and you sense the vibration, it could be in the motor as well as the flexplate or torque converter on an automatic, and perhaps as far back as the input shaft of the tranny. All this stuff is still rotating while in neutral.

I am chasing something similar in my T with a SBC 350/TH350. I can go down the road in the RPM range where it vibrates, slip the gear in neutral and it instantly goes away - put it back in gear and as soon as it hits the 'right' range, you can sense the vibration again. In my case, the range is 2000-2500 rpm. Also, sitting still in neutral, you can feel it in the same rom range. It is not a strong vibration but if you are looking for it you can feel it.

I originally thought balancer, but the balancer on it now looks good with no visible cracks in the elastometer (still could be the balancer though I put that at a low percentage). I've eliminated pinion angle and driveline issues. I've pretty much determined that it is either a flexplate / torque converter issue or I've hit a natural harmonic with the frame. This will be looked at more closely this winter.

Good luck to you.

122Dave 09-05-2006 08:08 PM

Yeah I think your right about it being anything between the harmonic balancer and the torque converter. The give away is that the vibration builds up in second and then disappears when it shifts into third... but comes back as the rpms get back up to the 3000 range. When I was picking up the harmonic balancer from the machine shop the guy was telling me how if something is out of balance but is close to the center of the spinning mass it will not have a big effect. He told me how one time he lost one of the bolts holding the flex-plate to the torque converter (these being further out from the center) and it set up a vibration like the one I have. So I am going to try adding weight to the outer edge of the flex-plate and see if that makes a difference. I hope to find time to fool with it this weekend. Dave

lamothe1 09-06-2006 06:09 PM

It's definitly not in your drive line/rear end. Gota be the engine or tranny.

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