By this I mean, how does the rear end move up and down. The ends are attached to the body via the control arms, and they are approx 2' long. Then, the center is attached to the transmission mount via the torque arm and it is ~ 6' long. Now, the picture of the Spohn torque arm shows bolts for attaching to the differential, I assume everything is attached firmly and doesn't slide back and forth. So, how can it move? It seems to me that the difference in length between the control arms and the torque arm would create a triangulation that wouldn't allow the differential to move. It does, so I'm wondering what I don't know about how the rear suspension works. All this is part of a mental exercise in getting rid of the panhard bar. I can feel that thing when cornering and I want something that doesn't move the differential left to right as it moves up and down.

Thanks,
Dan

 

His torque arm has a sliding section that allows its length to change. The factory setup allows the arm to slide front to rear slightly in its bushing.

You can't really get rid of the panhard bar. That's the only thing that holds the rear end from side to side. If you can "feel" it, then there's something wrong with your car, and it isn't the design. It's supposed to be set up so that the bar is level when the car is at rest, and should move the rear less than ½" side to side at maximum travel, which is less than ¼ of what the tires flex (i.e. insignificant).

 

Well, I was thinking of something more along the lines of the chevelle suspension. If I'm remembering it correctly, the rear control arms are angled so they position the differential left to right. But, thanks for the info.

Dan

 

Chevelles had what, a 4-link suspension? with upper an lower control arms?

 

Well, the two control arms have the ability to pivot 110 degrees in reference to the body (if you flipped the body upside down and used the bottom as the place of reference, it'd make a crescent). Next the rear axle is attached to the body by the rear shocks. These keep a stable pressure down on the rear. It then rests on springs that dictate the ride height and how bouncy the rear is gonna be. The torque arm acts as more of a lateral spring than a connection. As you can see, its attached by a rubber mount that allows movement, and is also usually of a composition that allows the metal of it to bend, thus acting like a spring to keep the rear stable.

 

Right... a 4-link with 2 angled control arms (the uppers in the case of A & G bodies,as well as B, C, etc.) uses the uppers to locate the rear from side to side. The lowers are more or less perpendicular to the axle, like they are in these cars.

The shocks don't keep any significant amount of pressure on the suspension. Their sole purpose is to act as viscous damping, so tha tthe natural resonance of the spring-mass system doesn't cause the body to bounce up and down indefinitely after going over a bump.

The torque arm is not a spring. It is supposed to be a fixed pivot much like a control arm. Its job is to keep the rear from rotating under torque. Since the wheels are attempting to turn in one direction when power is applied, the rear housing tries to turn the other way; something has to restrain it. Aftermarket torque arms eliminate the flexibility of the factory one, which dramatically improves the car's behavior under power (the only time when the TA is actually loaded).

There are racing 4-link suspensions that you can get for these cars, but of course you have to back-half the car to put them in. Most of them use 4 parallel arms for maximum freedom of motion, and a Panhard bar for centering.

 

You are right to question this, Chevelles came with leafsprings. There are aftermarket triangular 4-link kits availible for most muscle cars to accept this conversion.

 

Chevelles did not come with leaf springs. At least, none of the dozen or so that I have had did, nor the El Camino that I have now, or the Monte Carlos (G bodies, the same underneath as Chevelles) that I and my family members have had, etc. They have coil springs and a 4-link. So did all the other A and G body cars based on the Chevelle platform (LeMans/GTO, Cutlass, Skylark, Monte Carlo, Grand Prix, etc. etc.).

Novas and Camaros, and their derivatives from the other brands, came with leaf springs, until the 3rd gen F cars like ours.

 

Exactly. Going over to the dark side, all fox bodied chassis had 4 links also and even came with horizontal shock to reduce axle rotation and wheel hop. The 4 link is easier to design/tune, but is not as robust as the pan hard rod and LCA suspension.

 

Stable pressure, dampening pressure. The shocks exort enough pressure to stablize the rear don't they? If not wouldn't the rear end bounce until the air friction on the car and springs overcomes the elastic force of the spring?

And no the torque arm isn't a spring. But it keeps a force to rectify the rear-end, much like a loaded spring (which the stock ones are under constant stress, thus keep the pressure in the rear to keep it from turning). All the stock torque arms I've ever taken off (4) have been loaded and under pressure.

 

Shocks don't exert pressure. They are a damping thing, a resistance to movement. They work in fact by way of fluid friction inside themselves. They do not have anything to do with holding up the car, i.e. exerting pressure; if you took them off completely, the ride height would not change.

A spring is a thing that stores energy by bending. The torque arm does not do this, or at least it's not supposed to do it very much. The only reason it seems to be loaded when you take it off, is because the springs aren't centered on the axle housing. So if you support the car by the frame and let the rear hang, the springs will be trying as hard as they can to rotate th rear end. If, on the other hand, you jack up the rear an inch or 2 after you get the frame supported and then put a 2nd set of jackstands under the axle tubes, i.e. at the same point that the tires support it (the axles, i.e. the center of the axle tubes), you would find that there is no rotating force at all on the torque arm. If the driveline isn't trying to push the car around then there's no torque on the torque arm.

 

Oops, must admit this was a major faux-pa on my part, I was mistaking the Nova suspension for the Chevelle. Sorry.

 

No they don't. And no one I saw said that they did. No one said that they hold up the car, no one said they dictate ride height. The shock does exort force though. You wouldn't have loss of movement without a force in both up and down directions.

A torque arm is a torsion spring. A spring is anything that has memory enough to return to its original state, such as rubber-bands, basketballs, a wing, ect. Even a solid pipe could be considered a spring, even under your definition. say you had a vice on a tubular peice of iron, and your exerting x number of newtons on the peice of iron without bending it. At that moment the iron is exerting same x number of newtons at the teeth in the vice. The peice of iron, is now a spring. It is compacted (not noticable), and it holds energy. If it were to slip out of the vice, it would "pop" out. The torque arm is the same way. Though it may not "compress", it hold energy to stablize the rear-end by means of being a torsion spring.

 

I'm really not interested in arguing with you about this. I know how the suspension works, and what parts do what. I'm interested in sharing this information with people who are ready to listen. If you don't believe me, talk to any of the suspension parts mfrs, including the ones whose ads are on this page, they'll tell you the same things about how these cars work.

You need to go read some books on basic suspension design and modification, then you'll be ready to come back and answer questions on how they work. It doesn't help others to be spreading misinformation and semantic confusion.

The shocks do not "exert force", and the torque arm is not a "torsion spring". That isn't how those parts do their job. The shock is there for damping, i.e. it resists motion, as opposed to "exerting force" like a spring does; and the torque arm does not do its job by bending or "holding energy" like a spring does, any more than the frame or the control arms do their jobs by bending or holding energy. It is in fact a control arm within the rear suspension. Its job is to be a suspension link, that is to say, a rigid piece of metal to control the motion of the rear end. The more rigid it is the better it works.