C3 rear ride height and halfshaft angle

[Scott Marshall]

I got a 72 small block coupe that I recently replaced all suspension bushings with poly and installed a new 9 leaf rear spring from Corvette Central (original was 9 leaf also). I also installed new rear suspension bolts that came as a kit. I have not torqued any of the rear suspension bushings or the plate that holds the spring to the diffrential. The problem is the rear of the car sits almost 2" too high. There is no interior in it yet and no fuel in the tank, but I don't think that would make 2" diference. I know not to torque the spring mount bolts until the car is at correct ride height. How do I get it down? I searched the Archives and read that people are getting longer spring to trailing arm bolts. I would rather not go that route. Are the halfshafts supposed to be completely level or are they supposed to be a little higher towards the diffrential?

[Joe L.]

Re: C3 rear ride height and halfshaft angle

Scott-----

Have you "rolled" the car on the suspension yet? The rear suspension will not normalize to its final ride height until the car has been moved on the suspension for a distance of at least 10-15 feet.

[John H.]

Re: C3 rear ride height and halfshaft angle

With my C2 at the design "D" and "K" heights as shown in the A.I.M., measuring the half-shaft angles with a magnetic angle-finder shows them running downhill at a 3-to-4 degree angle from the diff to the spindles.

[Scott Marshall]

Re: C3 rear ride height and halfshaft angle

I have rolled it back and forth in my shop about 10 feet 3 or 4 times. It just seems like the spring is really strong. I still have my old one. I think I may put it on tonight and see the difference. I bought the new spring shortly after I took the car to a body shop and the guy said I needed a new one. I guess I should have checked the suspension geometry values before I took his word.

[Bernard S.]

Re: C3 rear ride height and halfshaft angle

Hi Scott:

During my 71 restoration, I had the same problem with rear ride heigth. As it turned out the new "exact reproduction" spring was the cause. Finally took the spring to a blacksmith and he adjusted the arc. One of the many challenges with restoration.

[Patrick H.]

Re: C3 rear ride height and halfshaft angle

Agreed.

I've got the exact same spring that came on the rear of an otherwise original 72 I purchased in October. I also have the exact same problem.

Needless to say, I retrieved the original spring from the previous owner and will reinstall it. Thankfully I knew the car and spring both before and after he did this, so the retrieval was easy.

You are better off putting new liners in your original spring, and using the new spring end bushings you have.

Generally, I wouldn't have used poly. The only places I think it's valuable on a Corvette are the strut rod bushings (they wear frequently) and the rear spring ends (they otherwise looked used and smashed and cracked a month after installation if you use the rubber ones). That's it.

Patrick

[Joe L.]

Re: C3 rear ride height and halfshaft angle

Scott-----

With the weight on the car and the suspension normalized, there should be very little, if any, positive arch to the spring. In other words, it should appear nearly flat with, possibly, just a very slight rise in the middle. If your spring currently in the car evidences a significant positive arch with the suspension normalized, then it's not right and that WILL cause the car to sit at a higher ride height.