1970 dart swinger vibration through car

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Mick65

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Hi all. Really need some help here. Just had A833 rebuilt, new pilot bearing , throw bearing, new clutch and pressure plate. The car has a fairly significant vibration at 60-70 mph. No vibration revving engine in neutral. Feel vibration on accel and decel. I have changed everything in car, motor mounts, Tran mount, engine (proper flywheel and balancer), changed rear u joint, took out pinion snubber to neutralize pinion angle. The only thing I haven’t changed is drive shaft and rear end gears in 8 3/4. New bear axles though. The gears don’t whine or make noise but the diff and driveshaft are only things not changed. I didn’t change front ujoint but no noise from it.
Really frustrated with this resto. Tires and rims were balanced on a manual balancer. The front end has had new ball joints, etc. I can feel the vibration right through the car and shifter. Any help would be greatly appreciated.
 
unbalanced drive shaft? has to be beyond the flywheel, right?
 
Make sure the U-Joint is Centered in the Yoke...
The Newer Replacement Ones have Thinner C-Clips on them than the Older Style had.
If the Joint is Relaxed to one side it will shake.
 
Rmoore said:
Did it vibrate when you took it apart ?
Click to expand...
It vibrated even in neutral before but that is now fixed with new flywheel and clutch. Now it only vibrates through car and shifter at 60-70 mph
 
eekvonzipper said:
Make sure the U-Joint is Centered in the Yoke...
The Newer Replacement Ones have Thinner C-Clips on them than the Older Style had.
If the Joint is Relaxed to one side it will shake.
Click to expand...
Installed a new ujoint at back but not the front one. I’ll double check it but I thought it was centered properly
 
What I would try is to get the car into the vibration zone, or a little beyond then clutch it and put it into neutral, and coast down thru the vibration zone. By doing this, you remove everything from the transmission forward.
So if it still vibrates, it is After the trans
So then my first question is, Is the driveshaft the right length?
If it is too short, then the front slip-yoke moves to the back, and the U-joint with it. If it gets too far out of the support bushing, then even a small imbalance in the front U-joint can set the slip-yoke to oscillating.

Good luck
 
A Reed Tachometer would really be handy here. Old school tech, but they flat out work for vibration diagnosis. There are several on ebay. I was very fortunate when I left one of the dealerships I worked for. They gave me all kinda of cool old tools and the Reed Tach was in the box. They will pinpoint what frequency the vibration is so that you decide if it is tires or wheels, or if it's drive train. Takes all the guess work out.

All of that said, describe the vibration. Is it a low frequency like a tire out of balance, bent wheel or separated tire, or is it a high frequency like a heard of pissed off bumblebees?
 
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