What engine is this 383 or 400 SBC or what ?

 

More likely the engine is out of balance, and the converters are magnifying it.

 

I agree with forcd. Sounds like u have a balance issue that maybe stems from your flexplate.

 

It's a rod piston ls6 fresh from the machine shop. The stock 5.3 I had in the car did the same thing.

I've change

Balancer
Converter
Flexplate
Engine

 

I remember when I installed a 6.0 in my car (truck engine) I used a vette front access. drive.
App. the vette balancer is bal. diff than the truck one was, and I had a bad vibration around 2500.
When I rebuilt it, I had it balanced and added an ATI balancer, now its smooth.

 

Weird since they're all neutral balanced and not keyed. If the Trans can't cause it I continue my search, just don't know it it's possible or not

 

What motor mounting system are you using?

 

Are dowel pins installed and are the transmission and engine actually mated? No gaps.

 

Yes all dowels and yeah bolts right up. Running aje k member mounts and their Trans mount which is basically solid. I tried buddies cross member which uses a big rubber mount and it still did it

I'm going to put that back on and I ordered an ati balancer

Internally can the Trans vibrate? If not I know to cross it off the list

 

There are rotating components inside the transmission. But for them to 'go out of balance' without a major breakage occurring would be extremely rare, imo.

 

Figured. Problem is just odd since I've even changed engines

 

Ok ..... you say this vibration occurs at around 2500 rpms. Is that with the car running down the road OR with you holding the rpms steady with the car in park?

 

Both, equally bad. All 3 gears, neutral, park

 

You said that it didn't vibrate when the conv wasn't bolted to the flexplate, but did vibrate when it WAS bolted to the flexplate. If this is correct, then that tells me the issue is in the trans. And would explain the vibration behind two different engines.

 

it doesnt vibrate when I have the trans unbolted from the mount, so it leads me to think its trans. But if a trans really cant cause it, then its not the case. My next step after ati balancer and diff mount is trying a friends th400

 

it doesnt vibrate when I have the trans unbolted from the mount, so it leads me to think its trans. But if a trans really cant cause it, then its not the case. My next step after ati balancer and diff mount is trying a friends th400

That is very weird.

 

Have you tried clocking the converters? I have one from Continental that has had a vibration in 2 different vehicles, 2 different th400's and 3 different engines. Usually find the sweet spot and it's vibration free.

 

Specifically no, thought it did the same thing on 3 combos. I have a ptc in it now and same thing so I don't think it's the converter

 

Torque converter balance issue.

 

I swapped converters

 

Bell housing flush with block?

 

flush with the block. I just feel like the trans being fully bolted up transmits the vibration worse. Im going to change over from stock to an ATI balancer as soon as it comes in and swap crossmembers

 

Anything new?

 

interesting and curious for the results

 

If this vibration happens when you have the whole drive train rotating..

Then I would say that your pinion angle is off.. Or there is NO pinion angle..

 

Just went through something similar like this, coul've sworn it was either the tranny or the transfercase. It was the u joint. Even doing it looked like there was nothing wrong with it. So my advice: take out the drive shaft and have a good, hard look at the u joints.

 

Posts #13 & 14 ..... he sez it happens in park and in neutral.

 

Does the converter snout engage the crankshaft? How much clearance between the converter and the flexplate, when the converter is fully seated in the pump? It sounds like you could be pulling the converter too far forward, or the snout isn't seated in the crankshaft far enough.....the flexplate bolts were never designed to "align" the converter only fasten it the the "flexible" flexplate. The alignment part is done with the crankshaft pilot hole and converter snout.......if they are misaligned, they will get gyroscopic with increased rpm causing vibration.