Solve one problem, give yourself another....

[antijam]

In common with many C3 owners I found the stock rear camber cam adjustment at the inboard strut mount fiddly to set and liable to drift under road shock loads. Accordingly I replaced the fixed length struts with adjustables, these having opposite hand threaded rod ends allowing them to act as turnbuckles - rotate the strut in one direction to lengthen (induce negative camber) and in the other to shorten (induce positive camber). After setting the correct camber the strut length is locked by tightening lock nuts at each end. The stock struts are fitted with rubber bushes at each end which are prone to wear and in the adjustables I chose the bushes are polyurethane to give longer life.
After setting the camber roughly correct myself I had a professional alignment done on the rear end to set both camber and toe to factory spec. A few weeks later while glancing at the rear of the car I noticed that the negative camber on the left side was obviously greater then that on the right. A check revealed that both lock nuts on the strut were loose and it had obviously 'unwound' to increase the negative camber.



I have faith in the competence of the tech who did the set up and it's very unlikely that he neglected to tighten the locknuts after adjustment. I think the problem resides in the fact that as the trailing arm rises and falls it imposes a torque on the strut. In the original struts this torque was reacted by distortion in the rubber bushes; in the adjustables it is reacted in the stiffer poly bushes but it also tends to fret the rod ends, alternately applying tightening and loosening torques to the threads. I'm presuming this is what caused the locknuts to loosen.

A better solution than polybushes is to fit rod ends with Rose (Heim) joints instead. these will isolate the struts from applied torque. These are available and in hindsight are what I should have fitted instead - ah well! Until I can get them replaced I shall have to do regular checks on the struts integrity - in theory if loose, the struts could completely unwind causing collapse of the rear suspension - a situation best avoided!

 

[Forrest Gump]

I experienced the same thing with the locknuts loosening. As you say, it is the torsion in the strut rods during suspension movement that causes this - particularly when the rear of the car is jacked up. I put some Loctite on the nuts, did them up extra tight (they’re a pretty big nut) and haven’t had the problem recur since, fingers crossed.

 

[Oneball]

Rose joints are noisy and harsh and they wear quickly. There’s a reason manufacturers don’t use them in road cars.

 

[antijam]

I agree that Rose joints are generally best reserved for track cars where precision and easy adjustability is needed and certainly if a fully Rose jointed suspension were fitted to a road car it would make the ride very uncomfortable. In the case of the 'Vette strut rod a Rose joint would only be needed to eliminate torque on the threads. Perhaps an optimum solution would be to fit one only on the outboard end and retain a rubber or poly bushed end inboard where any harshness would be isolated from the frame?

 

[theseoldcars]

The entire rear end of my C4 was outfitted with rose joints and it was quiet, compliant, and lasted pretty well, too. Just my experience. Obviously, it'll differ from car to car, depending on what else was done. I still had plenty of sidewall and factory dampers and springs, for example. Did keep a box of spares, though, just in case.