Bent or improperly indexed or unbalanced driveshaft.
Brake drum dragging
As mentioned pinion angle
Brake drum dragging
As mentioned pinion angle
Drivetrain Vibration
- Thread starter jakuzzie
- Start date
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U can’t just balance the crankshaft and the balancer and flex plate. The pistons and rods need it also. U may of just made it worse. Did u have the motor out for balancing? Running in neutral or park car not moving then like stated it’s in the motor or tranny/converter/flex plate. Why no pics of the modified flex plate, balancer. Is the correct crankshaft in it. Have u verified it as such. If ur confident the motor is good that leaves the flex plate, converter and or tranny. But that may only be 1 of the problems as when driving that can and does create new vibes. I can’t for the life of me figure why u put the old converter back in when u knew u had these vibes. Post some dam pics if u want some fn help. Kim
Yes it´s the correct internal balanced crankshaft.
Obviously the crankshaft was balanced WITH counterweights (weight of rods + pistons) and WITH 904 flexplate (not modified) AND harmonic balancer.
BEFORE I had vibrations (car not moving) = ENGINE VIBRATIONS.
NOW it is only vibrating when the car is MOVING (neutral or in gear) = DRIVETRAIN VIBRATIONS.
BEFORE the crankshaft balancing i thought it´s the converter.
I bought a new one and after a short drive it broke down.
BUT it was the SAME vibration like before.
I described my problem many times before. (It`s an advantage to have the ability to fn read) ;)
Driveshaft had to be shortend for the 8 3/4 and it has been new balanced.
Also installed new brake drums. No improvement..
Pinion angle is right.
What is the trans angle? What is the pinion angle? And u measured this in the car? Sitting on all 4 wheels? If ur pinion angle is right ur trans angle is off. Kim
This has to be driving you nuts, i know it would cause sleepless nights for me.
There is 3 different speeds of rotating assemblies going on.
Engine
Driveshaft
Rear axles.
i think you have ruled out engine vibration,and driveshaft.
Tight spot between ring/pinion
Bent axle
Wheel with excessive runout.
when i set driveline angle, i jack vehicle under diff and set engine
At level. Then i check how far up or down pinion is. I do it this way to simplify it in my mind.
I have also run vehicles up to vibration speed on my hoist, but it terrifies me. And it adds other variables into it, no load for one.
There is 3 different speeds of rotating assemblies going on.
Engine
Driveshaft
Rear axles.
i think you have ruled out engine vibration,and driveshaft.
Tight spot between ring/pinion
Bent axle
Wheel with excessive runout.
when i set driveline angle, i jack vehicle under diff and set engine
At level. Then i check how far up or down pinion is. I do it this way to simplify it in my mind.
I have also run vehicles up to vibration speed on my hoist, but it terrifies me. And it adds other variables into it, no load for one.
I use the tremec app. As i mentioned its so much easier for me to make motor/trans level, then set diff a couple degrees down.
What did u set the angles at too start with? Did u set them the proper way? What are the angles now? Kim
512Stroker
We are all here because we are not all there.
Great video
I had this same isssue, it ended up being 2 problems.
My drive shaft was in balance but the driveshaft tube was out of round, even new tubes need to be corrected. I took it to 2 differant driveshaft shops before I found this out from the second shop.
The pinion yoke on my 8 3/4 was old and sloppy not allowing proper fit on the pinion gear splines. To the naked eye it appeared OK. After replacement of the yoke no more highway vibration.
512Stroker
We are all here because we are not all there.
If those were taken from the trans tail shaft and pinion yoke, those angles look right on. I would not change a thing.
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Those angles look decent but maybe 1* too much. Can u lower ur tranny 1 *? Unbolt ur drive shaft and turn it 1/2 turn and see if there is any difference. Kim
I could be totally wrong, but my understanding is you would want the tranny and rear to be at the same angle. They can be different in race applications where the rear winds up and then creates the same angle under load. In my eyes those angles you are showing are your problem. They have the tranny and rear at about 6 degrees different.
Watch the video above. They have a vibration when the angles are different.
Jack
Watch the video above. They have a vibration when the angles are different.
Jack
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I KNOW IVE said this before but,i had the same issues as you.i had 2 diff. shops balance the shaft,several u joints,still had a vibration`.new shaft from strange engineering and vibes were gone.might be something to look into. also if your trans is 3 degrees up towards the rear,the rear should be set at 5-6 degrees down.as per cass at dr diff,thats with standard springs,
512Stroker
We are all here because we are not all there.
Check to make sure that the drive shaft tube is not out of round.
The shaft can be in balance but if the tube is out of round it will wobble and vibrate.
I‘ll do that. Thanks
DRIVE SHAFT!! Have another shaft built at a different shop. Had a customer years back with the same issue. We put my driveshaft in his car to try and the vibration was gone. After measuring his we also found it was to long. It was good while in the air but bottomed in the trans while on the ground. What car do you have and what is the length of your shaft center of cap to center of cap. There is a shaft length chart for different bodies in the DC manual. Balancing the shaft doesn't mean its clocked or the ends trued they could be installed at a angle.
I did a swap from a 904 to 727 years ago and had a terrible vibration as well both in neutral and driving. Found the transmission I had had a casting on the extension housing that made it touch the trans tunnel after installation. Once I resolved that, the vibration was gone.
Ok, I‘ll check these things first.
Stupid question:
Is this the correct output shaft bearing for the 904?
904 Output Shaft Bearing 1.230" (1962-71) - A&A Transmissions
Stupid question:
Is this the correct output shaft bearing for the 904?
904 Output Shaft Bearing 1.230" (1962-71) - A&A Transmissions
Early a body
Well-Known Member
driveshaft bent , has a dent , or out of balance
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