Vibration Help...Drive Shaft?

BelAir64

BelAir64

Member
Hey Guys,

I have had a vibration starting around 55mph from the time I got my 63 Bel Air. It is a 283/PG and is all factory suspension except 1 coil cut off the front springs(rear is factory original) It feels a lot like wheels out of balance so I had that checked and had them checked to make sure they were straight as well. It had a bad bushing and the factory shocks still in place so I decided I must be getting some wheel hop or something at speed causing it. When I had it apart I decided to check the drive shaft and found a mess. It was 90ish(a little more actually) out of phase, bearing rubber was gone, and two of the three ujoints where junk. So, I replaced bushings, shocks and rebuilt the driveline.

Now, I thought the car would be smooth as glass. It is EXACTLY the same. The vibration might be a little tighter, but now I can feel it at a lower speed. It does come and go oddly enough through speeds. I can get it up to 60-65 some times and it is smooth, but the vibration will come back and I have to slow down to get it to go away. It does seem better after everything is warmed up.

I did notice that the drive shaft almost seemed too long when I put it in. When I put the drive shaft in I could barely get the bearing bolts started and the front yolk was bottomed out at the tranny. It seemed strange, but I wrote it off until the vibration was still there. I am wondering if there is some way a wrong driveshaft was put in at some point that is 1/4" too long or something. I can easily cut and rebevel the yolk, but I wanted to see if this sounds reasonable or if something else could be going on.
 
Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
If your yoke is bottoming out in the tranny tail shaft that is a disaster waiting to happen! There is some wiggle room adjustment built in the Carrier bearing mount. Drive shafts for these cars are different lengths for the stick cars and auto. You may have the wrong front shaft. That is the first thing I would tackle. Get that fixed and see if it helps.
 
BelAir64

BelAir64

Member
Makes sense for sure. Is the bearing usually somewhat centered on the slots? This one was at the very back. There is not a alot of slip room on the transmission shaft from a length standpoint, but I would think 3/8" to bottom should be sufficient...Thoughts?
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
You need to be about 1 inch away from bottoming out the yoke in the transmission.If you can't achieve this,you have something wrong in the way of parts.The front section of the drive shaft,or the front yoke is too long.Failure to correct this will result in transmission destruction.
 
ragtp66

ragtp66

Well Known Member
BelAir64 said:
Hey Guys,

I have had a vibration starting around 55mph from the time I got my 63 Bel Air. It is a 283/PG and is all factory suspension except 1 coil cut off the front springs(rear is factory original) It feels a lot like wheels out of balance so I had that checked and had them checked to make sure they were straight as well. It had a bad bushing and the factory shocks still in place so I decided I must be getting some wheel hop or something at speed causing it. When I had it apart I decided to check the drive shaft and found a mess. It was 90ish(a little more actually) out of phase, bearing rubber was gone, and two of the three ujoints where junk. So, I replaced bushings, shocks and rebuilt the driveline.

Now, I thought the car would be smooth as glass. It is EXACTLY the same. The vibration might be a little tighter, but now I can feel it at a lower speed. It does come and go oddly enough through speeds. I can get it up to 60-65 some times and it is smooth, but the vibration will come back and I have to slow down to get it to go away. It does seem better after everything is warmed up.

I did notice that the drive shaft almost seemed too long when I put it in. When I put the drive shaft in I could barely get the bearing bolts started and the front yolk was bottomed out at the tranny. It seemed strange, but I wrote it off until the vibration was still there. I am wondering if there is some way a wrong driveshaft was put in at some point that is 1/4" too long or something. I can easily cut and rebevel the yolk, but I wanted to see if this sounds reasonable or if something else could be going on.
Click to expand...


When you said the driveshaft was 90ish degrees out of phase did you "fix" it and put them in phase? I ask because take a look at the attached picture of the Front half of the shaft coming out of the trans and you will see the factory the front driveshaft IS roughly 90 degrees out of phase and I have 3 spare driveshafts and they are all set up the same way. I recently had my driveshaft re-tubed and new joints pressed and balanced and made sure to point out to the shop that I did NOT want them to change the phasing even though the guy at the driveshaft shop was insisting that it was wrong. My feeling is there has to me a reason GM engineers did it that way although what that reason is I have not yet figured out.

Chris58DriveshaftPartsBook.jpg
 
BelAir64

BelAir64

Member
ragtp66 said:
When you said the driveshaft was 90ish degrees out of phase did you "fix" it and put them in phase? I ask because take a look at the attached picture of the Front half of the shaft coming out of the trans and you will see the factory the front driveshaft IS roughly 90 degrees out of phase and I have 3 spare driveshafts and they are all set up the same way. I recently had my driveshaft re-tubed and new joints pressed and balanced and made sure to point out to the shop that I did NOT want them to change the phasing even though the guy at the driveshaft shop was insisting that it was wrong. My feeling is there has to me a reason GM engineers did it that way although what that reason is I have not yet figured out.

Chris
Click to expand...

In looking at the picture, I think I did set the driveshaft up like it is shown. Previously, the shaft was setup so that the front yoke of the front drive shaft was almost 90 degrees out of phase with the rear yoke of the rear drive shaft. I say almost because as the splines are on the shaft, it was not possible to actually hit 90...was closer to 100 or just over. So, I rotated the removable yoke and rotated it back to the point where the front shaft front yoke is lined up with the rear shaft rear yoke. From all I could find this was correct. I am second guessing a little but, though, and wondering if I lined up the transmission yoke with the rear yoke. I am going to have to look at that again.

Also, I unbolted the driveshaft from the differential at ride height and I was able to use a prybar to move the shaft back and forth at least 3/4", so I am confident it is not bottoming out.

I also checked for run out the best I could and I would say I have .020-.030 at the differential and about 1/2 that at the center of the rear shaft. I could not figure out a good way to check the front. I know zero is ideal, but I cant imagine a light, small diameter shaft causing that much vibration at speed...maybe I am wrong? The shaft is original as best I can tell and the run out is basically caused by the yoke end being slightly off center from what I can tell.

I am beginning to wonder if the tires shop I went to did not properly check balance or simply did not do all the wheels and tires.

I am up for any other ideas
 
yellow wagon

yellow wagon

Well Known Member
Supporting Member 2
Have you checked the front drums for out of round or dragging? A front drum that is adjusted too tight will surely cause vibration, front end shake etc
 
Jim Sullivan

Jim Sullivan

Well Known Member
Supporting Member 10
BelAir64 said:
I have not. I guess just pull the wheel and check for intermittent drag as it rotates?
Click to expand...
Just Jack the front tires off the ground and spin the wheels. You'll feel it if the drums are out of round and if the brakes are adjusted up properly. No need to pull the wheels off to check.
 
yellow wagon

yellow wagon

Well Known Member
Supporting Member 2
^ This. And out of round drum needs to be turned at a minimum. If its really bad then it will need to be replaced.
 
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