Brand new converter causing vibration?

[standup303]

Always something! The problems don’t stop. I’ll probably have a post about overheating tomorrow! Gonna try to make this short.

Had my 440 rotating assembly balanced by the machine shop including flex plate and neutral balance converter during the build process. Was a stock flex plate they welded washers to for balancing. Zero vibrations from the setup. This was with a Hughes 2500 stall.

Ordered a Dynamic 9” 3800 converter and got a B&M flex plate for external balance 440. Car had a bad vibration with this.

So I swapped the flex plate out to the one the motor was balanced with. Well the damn car still has the vibration.

I looked all over the new converter, no weights. I had to drill the 3/8” holes on my balanced flex plate out to 7/16” for the 3800 converter because the washers they welded blocked the 7/16” holes. So I couldn’t put it back with my original converter if I wanted to since it uses 3/8” bolts.

This has also caused a small amount of ATF to start leaking out of what I believe is the front pump seal due to the converter wobbling around.

Going to call Dynamic Monday to see what they suggest but wanted to see what you guys thought I could try?

 

[jimmack]

It has to be the converter you really did not say if he 440 was balanced internally or externally. Is the crank cast or steel if it's cast then its externally balanced if its steel then its internally balanced. When you got it all back from the machine shop did they drill holes in the crank and add Mallory metal to internally balance it?

Does the damper wheel on the front of the crank look like it has extra weight made into it that would offset balance it if its thin and uniform all the way around (No weird shapes in it) then it's internally balanced from the factory. If your seeing trans fluid leaking around the front seal of the trans odds are that the flex plate and or converter are out of balance. Find out from the machine shop if the crank is internally balanced or externally balanced.

 

[abodyjoe]

Had my 440 rotating assembly balanced by the machine shop including flex plate and neutral balance converter during the build process. Was a stock flex plate they welded washers to for balancing. Zero vibrations from the setup. This was with a Hughes 2500 stall.

Ordered a Dynamic 9” 3800 converter and got a B&M flex plate for external balance 440. Car had a bad vibration with this.

sure it isn't the flexplate?

 

[jimjimjimmy]

it sounds to me you have an external ballanced engine and a nuteral ballanced converter if the vert was externaly ballanced there would be a weight on it somewhere .

 

[MV8]

Converter should align/pilots off the crank hub, not the flex plate bolts so you can switch back to the old converter and balanced flexplate with the 3/8 holes opened up to 7/16.

I wonder if the new converter is a close fit to the crank. With all the flexplate bolts in but a few turns loose, try moving the converter up-down-sideways to feel how close the converter pilot OD fit is to the crank hub ID.

The finger tight assembly on the motor can be checked for converter hub runout with the trans out of the way. Pull all the plugs and hand rotate slowly while making a video of the gauge at the back. Adjust, repeat.

Mag base dial indicator for checking runout:
Pardon Our Interruption...

 

[standup303]

It has to be the converter you really did not say if he 440 was balanced internally or externally. Is the crank cast or steel if it's cast then its externally balanced if its steel then its internally balanced. When you got it all back from the machine shop did they drill holes in the crank and add Mallory metal to internally balance it?

Does the damper wheel on the front of the crank look like it has extra weight made into it that would offset balance it if its thin and uniform all the way around (No weird shapes in it) then it's internally balanced from the factory. If your seeing trans fluid leaking around the front seal of the trans odds are that the flex plate and or converter are out of balance. Find out from the machine shop if the crank is internally balanced or externally balanced.

Cast crank externally balanced. Using the factory style harmonic balancer, it’s in decent shape and does not appear it has moved. I do not think the crank had metal added to it. It was 2 years ago. I’ll look through old pics though.

 

[jimjimjimmy]

if i understand you right there would be no weight added to the crank if it's externally ballanced .

 

[standup303]

if i understand you right there would be no weight added to the crank if it's externally ballanced .

From the factory my crank was externally balanced, and I’m 99% the new converter is neutral balanced. I am not sure how the machine shop balanced the crank and flex plate. But it worked fine with a different neutral balance converter.

So not sure why the same crank and same flex plate wouldn’t work with a different neutral balance converter? All I could think is to buy an internal balance flex plate like a B&M 10230 and try it out.

I’m going to call Dynamic tomorrow and see what they think. I’m doubtful those guys put out an unbalanced converter. So I’ll have to see what they recommend.

 

[Murray]

Oil leak is probably the vent.

 

[jimmack]

Cast crank externally balanced. Using the factory style harmonic balancer, it’s in decent shape and does not appear it has moved. I do not think the crank had metal added to it. It was 2 years ago. I’ll look through old pics though.

What year is the engine.

 

[496 polara]

Wouldn't you need a weighted flexplate for use with a neutral converter?

 

[Bewy]

Weren't weights added to the c'ter for external balance engines...not to the f/plate?

 

[standup303]

Ya so the BM external balance flex plate has a half moon cut out of it. The one from the machine shop was a neutral balance flex plate the shop just welded weights to.

Called the machine shop and he said if I tried 2 different flex plates and the new converter vibrates and the old one didn’t then it’s gotta be the converter. Going to take it out AGAIN this weekend, volt the old one back in and be 100% sure before hitting up Dynamic for warranty.

 

[jimjimjimmy]

any updates ?

 

[standup303]

any updates ?

I haven’t messed with the converter at all. In the middle of a bedroom remodel right now. I will post up when I get the old one installed and see if that one vibrates.