[Cameron]

Before this weekend, I had been experiencing a vibration in the shift handle that started at aroun 75-80 mph. Having the drive shaft balanced helped, but did not cure the problem. This weekend, I started playing with drive line angles. The tranny is pointed down at 4 degrees while the pinion was down at 1 degree. I added some 2 degree shims between the leaf springs and and the rear end and brought the pinion up 2 degrees. I also eliminated the Poly spring pads to prevent flex. Now, the pinion is point up at 1 degree and the tranny is pointing down at 4 degrees. The vibration has gone away and now waits until the car gets to around 90mph or so. The intensity of the vibration has gone down some too.

Anyway, on to the question. Obviously, I need to further adjust my pinion angle, the question is how do I do it? Another 2 degree shim would bring the pinion angle and the tranny angle to within 1 degree of being parallel. The problem is, that if I stack two, 2 degree shims between the leaf spring and the spring pocket, the locator pin that sticks out of the spring (I have Hotchkis leaf springs, if that matters) isn't tall enough to go through both shims and stick out of them enough to engage the hole that is in the spring pocket. What are my options here? Are there 4 degree shims available that have a hole for the locator pin on the spring and that also have a locator pin on the other side to locate the spring pockets? Is there another solution?

[HwyStarJoe]

Cameron,

Did you think about shimming the trans mount also to bring it up a couple degrees? I suppose if there's not enough room in the tunnel, that wouldn't be an option, and might affect the shifter position.
Has anyone shimmed the trans mount or even the crossmember a degree or two without problems?

[Cameron]

Yes, I have considered that and I have tried it. Since the drive train is hinging on the motor mounts and I am adding shims a few feet away from the hinge point, there is very little room to make changes to the angle itself. I added a 3/16" shim under the trans mount and I couldn't detect any change in output shaft angle.

[rickmack]

Where did you get the shims? I need to do the same thing to my car.
Thanks

[bretcopsey]

Would using a longer center bolt be an option? You would probably have to put some washers/spacers under the "head" of the bolt to keep it up high enough.

Check out this link:
http://landrumspring.com/racing/accandparts.html#center

[GMJim]

Cameron
What ever the angle of the trans to shaft is eg. 3* negative, the pinion to shaft angle should cancel it eg. 3* positive. Besides, if you try to get a zero zero angle, it will change as soon as you fill or empty the gas tank. Usually driveshaft vibration is felt at lower speeds. What is the condition of the tail housing bushing? A vibration like this can be caused by a worn bushing or yolk or both. Assuming the U joints are installed properly and the flanges aren't bent from installing the joints with a hammer. I had a customer with the same problem. After he had another garage do everything, driveshaft balance etc. etc. we installed a $3.00 bushing and the vibration was gone.
Jim

[Cameron]

Rickmack,

I got the shims from Summit. Just do a search on Competion Engineering. The angled shims are one of their products.

Jim,

Tailhousing and bushing are new. U-Joints have less than 5,000 miles on them. I just had the driveshaft checked and balanced. Slip yoke is the one that came with the car. Pinion bearings also have less than 5,000 miles on them. I didnt' see any major wear on it. Everything should be tight and vibration free, but it isn't. Driveline angles are almost last on the list of things to try.

Also, adding the 2 degree shim between the rear end and the springs and the 3/16" shim under the tranny mount definitely caused a reduction in vibration. I think that I should at least investigate the drive line angles as a cause for my vibration some more before I rule them out.

Another source for the vibration might be drive shaft flex at high RPM. My only recourse for this would be to have a new drive shaft built that had a larger diameter than my current stock shaft. Right now, I would rather spend money on shims than I would a new drive shaft, even though it may come to that.

If anyone has any other ideas as to the source of my vibration, I would love to hear them. I am going to do some more testing so I can document exactly when the vibration starts, if it is more pronounced when I am heavy on the gas or gradually speeding up, etc.

[2SLO4ME]

Cameron take the drive shaft out of the car with car on level ground with equal size blocks under each wheel to where you can get under the car and measure with a angle finder the degrees at which the output shaft of the trans.is pointing and record it down on a piece of paper.Then go to the rear pinion yoke and turn it to a vertical position and measure the angle at which it is pointing and record it down.The 2 measurements should total 180 degrees.Depending on what kind of set-up you have on the rear-end you may want the pinion to point down a couple of degrees and sometimes a little more.Also draw a imaginary line coming out of your trans.output shaft,and then draw another line coming out from your pinion yoke.These two lines should be on the same plane and not cross one another.I hope this will help you out. [img]graemlins/thumbsup.gif[/img]

[Cameron]

2Slo,
Right now, my pinion needs to rotate up 3 degrees in order for the imaginary lines from the output shaft and from the pinion to be parallel.

I am going to try some more shims, but I will be in Bristol, TN from tonight until Sunday night so I won't be able to get to it. I'll let everyone know what happens. Hopefully, that will fix the problem. I will just have to get some spacers to go under the pin (bolt) so that it will be long enough to go through both shims and still stick out enough to engage the alignment holes in the spring pockets.

[HwyStarJoe]

Cameron,

Did you change the rearend by chance, and have to move or change the spring brackets? I thought about that when you first posted. I'm just wondering because the spring brackets on the axle tubes have to be welded on at the proper 4 degree angle.

Just throwing out ideas....

[Cameron]

Joe,
Yes, I did have to change the rear end last summer. I used an 8.5" 10 bolt out of a 72 Nova. I didn't change or modify the spring pockets though. Hopefully, I can get some time in the next couple of days to do some testing, but I think that the problem lies in the pinion angle.

[Cameron]

I think that I may be going about curing this vibration all wrong, so I started a new topic that is more related to vibration solutions rather than pinion angle adjustment. Go here http://www.camaros.net/cgi-bin/forum...&f=18&t=000148 to see it.

[bolandps]

Hi guys, I know this is an old post, but it was helpful. Curious what the final solution was? I am having the same problem, and after shimming the trans without much movement, I am now considering lowering the engine, wondering has anyone done this before?