Can a converter cause vibrtation?

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rfoll
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Can a converter cause vibrtation?

Post by rfoll » Sat Feb 17, 2018 5:41 pm

I have a Chevy C20 with a switch pitch 400 trans. During recent cold weather, the transmission had a whine when the engine was started, and it would take a few seconds to engage when dropped in gear. I did a flush and new filter, the problem went away, but the ambient temps had come up 20 degrees by then. My local trans expert suggested it might be the converter. The trans probably has less than 30,000 since the last freshen, the converter maybe 20,000 more since it was built. Running down the road there is a barely perceptible vibration that feels like driveline, and under hard acceleration it is severe over 4000 rpm. If I kick it in neutral at speed the vibration subsides significantly. I parked the truck, put it in gear on high stall and power braked it to 2500 rpm, and no vibration. I put it in neutral and revved the engine and it starts to vibrate around 4000 rpm. None of the vibrations were there 2 months ago. I'm completely baffled.
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lefty o
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Re: Can a converter cause vibrtation?

Post by lefty o » Sat Feb 17, 2018 9:21 pm

sure, there are multiple parts in a converter that can fail, without even getting into a ballooned converter.

F-BIRD'88
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Re: Can a converter cause vibrtation?

Post by F-BIRD'88 » Wed Feb 21, 2018 1:30 am

Put it up on the hoist.. Pull the three converter to flexplate attaching bolts and push the converter back in the pump... Fire it up and see of the vibration is still there when you rev it etc.
If the vibration is suddenly gone then the converter or the pump is suspect.
If the vibration is still there it is engine related. Flex plate, crank pulleys etc.

To check for trans and drive shaft rotational vibration jack the rear tires off the ground.
Jack under the axle, do not hang the rear axle. Use safety stands under the rear axle. Now start it up and run it in gear so the rear tires spin. Watch for oscillating wheels.... Bent wheel rim. Axle, busted shifted tire cords... If it vibrates but wheels do not oscillate . Check drive shaft.

On the th400 the Auto trans flexplate is a common spot for failure. It cracks between the crank bolts on the flex plate. Often makes noise.

rfoll
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Re: Can a converter cause vibrtation?

Post by rfoll » Wed Feb 21, 2018 10:00 am

I found the driveline vibration. When I installed the driveline I got the phasing backwards. I mistakenly thought the picture was front to rear, the picture of what I thought was a trans was the differential. Very old factory manual.
So much to do, so little time...

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