Smokehouse69

This is more than one question, but primarily I'm try to figure out what is the biggest factor that causes C-3 steering to wander and get squirrely at higher speeds on uneven roads?
What's the most important factor in fixing this problem? I've heard so many opinions and fixes that I have become extremely confused on what are the actual causes. Is the wider than normal tires that so many of us are using? Is it just general wear on all the major steering and front suspension components or is it something specific like bad powersteering control valve or worn or misadjusted steering box?
I guess the reasons I'm asking this is that after examining the steering and associated suspension components on my car, I can't seem to find anything that seems unusually worn or maladjusted, yet uneven and grooved roads give me fits at highway speeds. My rag joint is fine and alignment is perfect, in fact on a nice flat surface the car will track straight for miles, but a strip of uneven bumpy highway, it is like trying to control a wild horse.
All opinions and suggestions will be appreciated.

Twin_Turbo

It's everything together IMO. However I think that the steering box is a total POS. The whole thing has the tendency to wear. There's 2 puny little bearings inside and a really short collar that supports the shaft. Some may disagree here but the bimmers and the merc have used recirculating ball for a long time and their boxes are much tighter than ours.

vettfixr

Here's a thought and I'm sure I'll be corrected if wrong. The Pitman arm connects to the PS control valve. The control valve has to have a little play in order for the arm to move the control left or right to control the flow of fluid to the ram. Doesn't this create a built in "play" factor into the steering. And if you're on a bumpy road doesn't the motion of the wheels and steering linkage effect this control valve? I mean if the road wheel is moved 1/4 inch in either direction wouldn't it cause the system to think that the steering wheel was moved and it should apply power in that direction? Like I said maybe I'm wrong but the whole system seems to be a Rube Goldberg. They would have done better putting an internally boosted steering box on the cars and forget about the drag and pull setup they have on them now. :rant:

Paul L

My problem was fixed by switching to late C3 alignment specs. Jim can advise. I forget the link. But my 1979 is straight as an arrow now on the highway. An amazing change just with an alignment.

*Edit*-I went with advanced street.
http://www.stingray.nu/tips/alignment.htm


[Modified by paul79, 8:44 PM 1/15/2003]

71roadster

I think one of the causes is the lack of significant caster. 2* to 2.5* isn't much compared to the 4.5* to 5* used on the C4 and C5. The VB Tubular upper A-arms have more caster built in so you can get to 4.5* easy. This is also the reason the car doesnt have a very strong on-center feel (the steerig wheel doesn't return to center very hard).

The box is the other reason. Thats why I am installing a late model integrated power steering setup in mine. Its a lot of work but I think it will be worth it.

But, tight steering/suspension components and a well adjusted box and a good alignment should work pretty good, even with wide tires. I have 255's all around and even in california, where I think they actually design the roads to challenge all the SUV's, it wasn't too bad for my car.

Chris

GTENIT

SMOKEHOUSE MINE IS DOING THE SAME THING, AND HAVE BEEN FIGHTING FOR THREE YEARS KNOW. SOMETIMES THE BACK SEEM TO BE IN THE FRONT ESPECIALLY WHEN IN THE TRUCK RUTS. CALL ROBIN WILKIE AT VETTE BRAKES HE GAVE ME A FEW IDEAS.
I DID ORDER THE UPPER A ARMS HAVENT RECIEVED YET BUT GOING TO HAVE IT ALIGNED TO THE SPEC HE GAVE ME . HOPE THIS WORKS.

Jim Shea

A lot of highways have what is called Truck Troughing. You cannot see the troughs on a dry road, but just a little rain will suddenly show narrow troughs running straight down the highway. Wide tires tend to span the trough but the width of a Vette tread is nowhere near a truck, so with minor motions right to left, you tend to jump in and out of the two troughs.

I was the Steering Competitive Analysis Manager at Saginaw for the last five years of my career. I had to drive a different car or truck from all the other GM competitors every weekend. Tough job but somebody had to do it.

I did find that brand new Supras, Merc CLKs, and other sporty vehicles tended to track and then suddenly self steer in and out of truck troughs. I did notice this same type problem with C5s as well.

That's not to say that the steering system in the C2/C3 Vette can't be improved by reducing clearances in the gear, or that the control valve might be contributing to the problem.

I do remember one thing. Saginaw tried very hard to get Chevrolet engineering to change from the control valve type assist to an integral 700 model power steering gear on the C3s. (Corvette was the only passenger customer for the control valve and assist cylinder). We were always told that Chevrolet engineering felt that the control valve assist gave more road feel and therefore they would not change. (Maybe the bean counters really wouldn't let them make a major change to the frame mid cycle, I don't know.)

That's not to say that changing the caster and camber on a C3 with wide tires won't help. BTW these are the numbers for the C2 and C3 published by Vette Brake and Products Inc.:
DAILY DRIVER
Front: Toe 1/32" in; Camber 0 deg neg; Caster 2 3/4 deg pos
Rear: Toe 1/8" in; Camber 0 deg neg

ADVANCED STREET
Front: Toe 0; Camber 1/4 deg neg; Caster 2 3/4 deg pos
Rear: Toe 1/8" in; Camber 1/2 deg neg

AUTOCROSS BASELINE
Front: Toe 3/16" out; Camber 1 1/2-2" neg; Caster 2 3/4 deg pos
Rear: Toe 1/16" in; Camber 3/4-1 1/2 deg neg

zwede

My thoughts on this (and I hope Jim will give his input in case I'm wrong) is that the alignment is very important. Assuming the suspension is in good shape, I would carefully consider Toe and Caster.

I don't agree with VB about 0 Toe in for a street vehicle. 0 Toe will make it darty and unpredictable on the highway. I would go with 1/8" Toe in for added stability. I'm running 1/8" Toe-in.

As for Caster, more is better. I have the offset upper A-arms and set caster to 4.2 degrees.

I find my 71 to be very stable at speed. Actually, I don't notice any jumping at all. Tires are 255/50-ZR17.

mrvette

zwede, on that castor thing....
I notice when setting up the suspension on my car, the offset for castor is damn close side to side...BUT....say the car is turned left...the driver's tire of course points our, and the castor on it appears say 5 degrees....on the pass side, it appears allmost straight....not quite, but allmost straight....
turn the wheels to the right....same thing pass tire is say 5 degrees but driver's tire is nearly straight....
MY question is...now in hell can that be??? if the ball joint center line is moved/inclined a certain amount...wouldn't the change in the wheel be the same but in the opposite direction when wheels are turned???
BTW, the camber is straight up and down....
I"m doing this in my concrete floor garage, with very careful attention to the car beind on level pads....with slick surfaces to turn on....slick enough I can easily turn the wheel by one hand with engine off....

GENE

Sean82

here are my .02
I have replaced all front suspension components, - tie rods, ball joints etc.
rebuilt ram, rebuilt control valve, pump, new hoses.
new flex coupling with flange
4 wheel alignment.
adjusted gear box - new seals and grease.

Still I have the same problem as you.
Now very po'ed.

I strongly believe that it is the steering gear. When you take one apart you can see the wear marks on the internal parts. I would like to get mine rebuilt but all they do is change the bushings and seals (heck I can do that).

I am going with the advice from Norval and Jim Shea, and I will have the box machined like they did in the "big block from Hell" project.
I have bought new bushings and ball bearings, as soon as I have the box out(again) I will be taking it to the machine shop!




[Modified by Sean82, 2:28 PM 1/16/2003]