I have a loud pop coming from the rear when accelerating hard from a stop. Most likely wheel hop correct? And if so, is the best way to eliminate that upgraded lower control arms and springs? Thanks. 1990 Camaro.

 

Third Gen's don't wheel hop. "Most likely" not. The torque arm pretty much makes wheel hop impossible. My car has a stock torque arm, stock rear suspension, 180k on the chassis, near 400 HP, a Torsen in the rear end, and I can't get it to wheel hop.

GD

 

Is your rear sway bar still on? and tight?

 

Wheel hop would shake the car to hell. Likely something else.

 

These cars all wheel-hopped MERCILESSLY from the day they rolled off the showroom floor.

It's due to flawed suspension geometry design; no doubt there was some other consideration that led to them setting the car up this way, maybe something related to the manufacturing process as opposed to vehicle operation, but I don't know what it is.

The root cause is that the instant center (the point at which acceleration force acts on the vehicle) is somewhere BELOW the center of gravity. In a suspension of the type we have, this point is located, viewed from the side of the car, where the line through the front & rear bolts of the rear lower control arm, crosses a vertical line through the torque arm mount. Lowering the car makes it worse: obviously the rear bolt is fixed in height by the wheels & tires, but the front bolt gets closer to the ground, making this line point DOWNWARDS toward the front of the car. The IC ends up below the ground surface.

The ideal point for the IC is somewhere along a line from the rear tire patch to the CG, usually somewhere close to the CG. Rule of thumb for CG location is the shifter ****... not very precise of course, but it makes a good illustration. Proper location of the IC makes the suspension "neutral" under acceleration; it neither "squats" nor "raises". Not that any of us are ever going to get our cars like this, but to get an idea of what it looks like when this design is RIGHT, go watch a video of a Pro Stock in slow motion when it leaves. The suspension is very "quiet": the rear neither squats nor raises, the nose lifts slightly (usually not off the ground), and the car just GOES.

What the malfunction in these cars causes to happen is, when you give the car gas suddenly, the rear of the body tries to drop (squat), because the "pushing" point on the body is BELOW the CG. It can only do this just so fast, specifically, the acceleration of gravity. So instead, the force compressing the springs tries to raise the rear axle off the ground. This reduces the force on the tires, causing them to lose traction. This reduces the accelerating force, causing the "squat" to go away. The springs push the tires back down, causing them to regain traction. The acceleration force is restored, causing the car to "squat" again. Over and over and over, at a rate of about 7 or 8 instances per second in most of our cars with stock (or near stock) rear springs. You can see the result in the tire tracks the car leaves on the pavement: looks like a series of dashes.

Needless to say, this is VERY hard on parts. Particularly, the transmission mount; because that's in the chain of things that holds the torque arm still, preventing the rear axle from rotating, and it gets literally HAMMERED apart by all this.

The cure is LCA lowering brackets. These lower the rear attachment point of the LCA, allowing it to point slightly UPWARDS instead of DOWNWARDS toward the front of the car. (emphasis on SLIGHTLY) the line through the 2 bolts then intersects the vertical line through the torque arm mount somewhere closer to the CG, thus applying the forward force of acceleration to the car in such a way that the body doesn't try so hard to rotate (squat) and lift the axle off the ground. It's possible to set it up "perfectly" with certain aftermarket TA setups, but this tends to make the car wheel-hop BAD under braking, which of course is an acceleration in the other direction. But it's quite easy to make a VAST improvement to the factory's already defective geometry, which just gets worse from lowering, either deliberately or from the natural sagging of the springs from old age.

Here's a really bad photo of the ones in my car. Note how the LCA in the photo is closer to the ground at the axle end than it is at the body end, by maybe ¾" or so. Somewhere around that angle is about right; level puts the IC right about at the trans mount, and 1" puts it above the shifter ****. Something around ½ - ¾" is about right in most circumstances.



Most likely your "pop" is from the transmission mount being broken in half. That's the first thing I'd suggest looking at.

 

I was going to suggest check your rubber trans mount but I was beaten to it. Also check that your exhaust isn't getting hit/squished as the car squats under acceleration

 

Idk about all that. All stock, high mileage parts mine wouldnt really hop unless it was top of 2nd gear when it broke free. Did all rod end control arms and panhard bar with a new rear and detroit locker. Made it almost undriveable (see pic) absolutely violent. This summer I switched to koni yellows, eibachs and a midwest chassis torque arm. Its much better. But still gets bad when under certain conditions. Maybe its somethin with the locker, thats when it got bad. But to say they dont wheelhop is a potential gross understatement

 

Interesting. I have a Torsen in mine and otherwise stock rear suspension and stock springs. I do burnouts basically daily. Never experienced wheel hop.

GD