[Gil Gomez (Cuda81)]

hello group
balanced 440,steel crank,auto,355s.
i have a rhytmic vibration problem @ hwy speed
ive changed third members,two drive shafts,both balanced & rebalanced,brute u-joints,urathane trans mount,axles,axle bearings,convertor,changed tires,wheels,pulled belts,changed harmonic balancer & even told my girlfreind to get out of the car! still no change
except im in the dog house
in neutral it not as bad,but if you rev the engine you feel it in the slap stick.
any suggestions would be appreciated
thanks gil

[Hans (72challenger)]

Ouch, looks like you already spend a lot of money to get rid off that vibe. Did you messed something up with the internal & external balancing? My mate has experienced the same problems, his internally balanced 273 was backed up by a 727 w/ externally balanced converter. You know, the one with the litlle weights placed at the front of the converter? He got these weights of the converter and the vibration was gone. Can't think about more causes. Good luck

[Dave-R (Roppa440)]

Well you just eliminated most of what you changed with that one statment that says "in neutral it not as bad, but if you rev the engine you feel it in the slap stick"

If the vibration can be felt when reving the engine, or it starts at the same rpm no matter what gear you are in, then the problem is with the engine and not the trans back-over.

When you had it balanced, did you have the harmonic balancer, crank, rods, pistons, flex plate and convertor all done together? You should have.

Also make sure the crank pully has not been bent or damaged in any way and is seated well. I got rid of most of my vibration just by cleaning the paint off the back of the pulley and re-fitting it! I think it was a paint run on the balancer that was doing it. It don't take much to throw things out.

[Gil Gomez (Cuda81)]

hello
yes i had everything balanced,although the convertor(no weights)is nuetral.i really dont feel it in park,while reving the engine.i feel it on the road in nuetral while reving the engine to the same rpm's. when i let off accellerator it like a dragging vibration,then upon accel @70 mph it sets up a rhytmic vib,then as i go faster its a constant vib.(just like a bad u-joint)i feel & hear it in the console area.somebody told me trans out of wack,bent input shaft,bent or cracked flexplate.i checked the flexplate when i pulled out my 3000 stall & put the factory hi stall.
the rear bushing feels ok.i changed the harmonic,no change. i'll check the paint,i doubt it though.
yeah the machine shop said they'd gladly check it.no problem right.
the problem did start after i installed the engine back in.what happened is that i had just 750 miles on my motor.
the napa rep. talked me into that purple syn oil.i didnt make it home it spun a rod.so i had to pull the motor change a rod and the crank,i dint want a 10m 30r crank.its been vibrating ever since,before i could go to 120 smooth as glass.i just dont want to pull it,then tear it apart and they tell me everything checks out ok.
any other input would be appreciated,before i pull it.
thanks gil

[Dave-R (Roppa440)]

I have to tell you that mine vibrates as well and I have been unable to find the problem.

Mine is totally speed dependant and not rpm. It starts at 80mph or so, getting worse as speed increases, and is cyclic in nature. I feel it most in the console area and it started after I put the engine back in. So if you find your problem tell me!!

I will tell you one thing you could try. Check the pinion angle to the driveshaft as this can cause this if not right.

Street car with stock springs = 2-3 degrees.
Drag racer and street car with SS springs = 5-7 degrees.