This is an update for the techno geeks. If you like looking at pretty pictures, stop reading now, and move on. If being diligent about every little technical detail of your car is something that you enjoy doing, than please read on.
Ever since I have owned my car, all 23 years, I have had some sort of vibration in the driveline at speeds about 70 MPH. Most of the equipment on my car has changed numerous times. The only constant being the ride height. In recent weeks I have really been studying what actually happens with these cars when they are lowered. I give a lot of credit to Troy, I forget his user name here. LOL He and I have exchanged some messages back and forth and he has really helped me to understand what it will take to make my car smooth. This is a thread that he started on Chevelles.com:
http://www.chevelles.com/forums/showthread.php?t=213271
There is also another great website that I used:
http://www.vibratesoftware.com/html_...aft_Angles.htm
This is by far the best website for explaining and measuring driveline angles.
The problem with GM A-bodies is that as the cars are lowered in the rear and front working angle increases dramatically. While it is possible to match the the rear working angle to the front working angle with adjustable upper control arms in the rear, this still does not address the problem of just having too much working angle.
I have no doubt that I will get 10 different opinion on this post. There seems to be a lot of conflicting information when it comes to driveline angles. I feel that the information in the above website is the most accurate that I have seen to date.
For the sake of this discussion I will always refer to something pointing UP when it is pointing from the back to the front of the car. Like this:
[front] \ [rear] = UP
[front] / [rear] = DOWN
I made a spacer which raised the back of the transmission about 1/2". My final readings were as follows:
Transmission: 2.5* UP
Driveshaft: .3* UP
Pinion: 2* DOWN
Front working angle: 2.5 - 0.3 = 2.2*
Rear working angle: 2 + 0.3 = 2.3*
I ran the car on jackstands and took it up to about 4000 RPM in 6th gear, which is over 5000RPM driveshaft speed. It seemed very smooth. Much more so than at other setting. The ultimate test will be how the car feels at speed.
Andrew