Vibration Question

[ricks70dart]

Asking for a friend,He has installed a rebuilt 727 and rebuilt torque converter behind his 340 which is in a 69 Dart.He has a vibration when revving in park and when driving on freeway speeds. Could this problem be the rebuilt torque converter not balance correctly. Any input would be greatly appreciated Thank you Rick

 

[Murray]

Yes, definately. I've had same issue. Removed converter and company balanced it (you could now see the weight welded to it), reinstalled it with no problem. Then it threw the weight off. Now I no longer do business with that company.

 

[TrailBeast]

Asking for a friend,He has installed a rebuilt 727 and rebuilt torque converter behind his 340 which is in a 69 Dart.He has a vibration when revving in park and when driving on freeway speeds. Could this problem be the rebuilt torque converter not balance correctly. Any input would be greatly appreciated Thank you Rick

Absolutely.
There are three things that can have an effect on balance.
Engine rotating assy, converter and flex plate. (and harmonic balancer in the front) but we'll skip that assuming for now it is the right one.
If the engine (rotating assy) requires external balancing, it needs a balanced converter or a balanced flex plate.
Either one could have the balance weights.

He could have balance weights on both as well, which would also cause a vibration like you describe.

340's are internally balanced so if the converter and trans were from a 360 or 318 there's the problem.

 

[Tooljunkie]

He would need to know if the 340 crankshaft requires external balancing. If so, torque convertor needs a weight added. Best to refer to old torque convertor to verify. A flex plate for external balanced cranks is also available.

Or,if new torque has a weight on it, it can be knocked off if crank is internally balanced.

 

[ricks70dart]

Absolutely.
There are three things that can have an effect on balance.
Engine rotating assy, converter and flex plate. (and harmonic balancer in the front) but we'll skip that assuming for now it is the right one.
If the engine (rotating assy) requires external balancing, it needs a balanced converter or a balanced flex plate.
Either one could have the balance weights.

He could have balance weights on both as well, which would also cause a vibration like you describe.

340's are internally balanced so if the converter and trans were from a 360 or 318 there's the problem.

Thanks we will do some investigation on the converter so if I understand correctly. The converters are different depending on cast crank verses forged,internal verses external balancing

 

[ricks70dart]

He would need to know if the 340 crankshaft requires external balancing. If so, torque convertor needs a weight added. Best to refer to old torque convertor to verify. A flex plate for external balanced cranks is also available.

Or,if new torque has a weight on it, it can be knocked off if crank is internally balanced.

Thanks for the info

 

[OL DODGE]

I bought a 77 Volare Road Runner with a 318. The guy had put a 727 and a 340/360 cast crank converter in it and couldn't figure out why it shook when he sold it to me . I drove it a couple of days like that and couldn't believe how bad it vibrated -at 35 mph it felt like your teeth would fall out. After the weights were popped off it, it was smooth though. I snapped them off by wedging a screwdriver under them and prying.Probably not "by the book" but it worked.

 

[ricks70dart]

I bought a 77 Volare Road Runner with a 318. The guy had put a 727 and a 340/360 cast crank converter in it and couldn't figure out why it shook when he sold it to me . I drove it a couple of days like that and couldn't believe how bad it vibrated -at 35 mph it felt like your teeth would fall out. After the weights were popped off it, it was smooth though. I snapped them off by wedging a screwdriver under them and prying.Probably not "by the book" but it worked.

Thanks

 

[AJ/FormS]

Asking for a friend,He has installed a rebuilt 727 and rebuilt torque converter behind his 340 which is in a 69 Dart.He has a vibration when revving in park and when driving on freeway speeds. Could this problem be the rebuilt torque converter not balance correctly. Any input would be greatly appreciated Thank you Rick

And the wildcard is just because the 340 is in a 69 may not mean it is a 69. and even if it was a 69 it doesn't mean 50 years later that the guts are still 69 spec.
So as already mentioned, go back to the last known smooth-running combo and check the balance of that TC; compared to the current one.
Good luck

 

[CudaFactHackJob]

If it's converter balance then it would shake more as rpm increases. Did you knock the distributor cap loose; or crack it?