Originally Posted by xp800

Just to clarify a few things on the structures side...dust off your Statics 101 books and get out a napkin for a free-body diagram if you need to.

The torque tube that couples the engine to the transaxle in the Corvette reacts ALL the torque generated by the motor to the differential; the body does not. This is the major benefit of this architecture. Typical front engine/rear wheel drive cars react powertrain torque with the body. So no matter how much torque the Vette motor makes, it won't "twist the car" on acceleration. There will still be the powertrain "inertial" roll torque from the rotational acceleration of the engine internals, but this relatively small and is reacted by the powertrain mounts as vertical forces (no fore-aft twist).

In fact, the powertrain is fully isolated from the body, so it does not add or diminish to global vehicle stiffness. And the loads into the body from the powertrain under acceleration are fundamentally from the tractive force at the rear tires' contact patches. These tractive forces are reacted by the suspension mounts to "push" the car forward, and the torque from halfshafts is reacted by the body mounts as a vertical force couple. This induces vertical bending in the powertrain (small, mostly contained in the torque tube) but does not "twist" the body.

The tunnel brace in the Corvette adds to global body stiffness as I mentioned before. It's a significant increase in both the bending and torsion moments of inertia. It forms a closed section with the tunnel helping both body torsion stiffness (like its own local torque tube) and vertical/lateral bending stiffness, increases local floorpan vertical stiffness by preventing the tunnel from 'breathing" (spreading open and closed), and improves side impact body integrity by distributing load to the non-struck side of the car.

The global vehicle stiffness is what we experience qualitatively as the feeling of "solidity" (or lack thereof) and handling precision (or lack thereof) from chassis/road inputs as well as engine vibration inputs. A stiff structure lets the suspension do what it needs to for better isolation and handling, and a stiff vehicle will tend to flex/vibrate less for improved NVH (and perceived solidity/quality). All the torque tube does is relieve the body from one of the largest force and vibration inputs.

All that said, leave the plate on. A thicker plate -may- help incrementally on a C7, but the tradeoff between added mass to added stiffness can go south faster than you might imagine. The previous generations of Corvettes were MUCH less stiff than the C7, and a it's quite believable that thicker tunnel brace produced a noticeable effect. But the C7 architecture is so much stiffer and the tunnel brace has been optimized in concert with this (by some smart folks...) to give the best thickness/mass for its intended effect.

/geek mode

Originally Posted by 10mm_

Are you suggesting the differential isn't connected to the body?

Originally Posted by xp800

It surely is. I called them powertrain 'body mounts' in my explanation. You could call them transaxle mounts for the rear and engine mounts for the front if you'd like; I was trying to keep it simple. My overall point was intended to differentiate a Corvette power train from something like a solid axle rear end.

Originally Posted by 10mm_

I'm not following how the car can't twist if the engine applies torque to the tube which applies it to the rear end which is connected to the body

Originally Posted by xp800

The engine applies torque to the driveshaft which applies torque to the transaxle which applies torque to the torque to the torque tube which applies torque to the engine. Net zero. These three main components are all rigidly connected to one another and causes the driveshaft torque to be reacted internally.

The torque tube has its name for this reason. It functions as the 'car body' in the front engine rear axle typical paradigm.

The torque that comes out sideways in the axles from the diff (and is reacted off the tire contact patches) causes the front of the car to lift and the rear to squat (from forces in the body mounts). But no twist is induced in the car body in the fore-aft direction.

Think of it this way if the above isn't working. Take the driveline out of the car. So now you have the engine-torque tube-transaxle assembly sitting there. Assume the diff is locked. When the engine applies torque to the drive shaft that spins the transmission internals that tries to spin the differential that's locked...nothing happens. Well nothing visible without instrumentation. In reality all that torque is winding up the torque tube, but even at full 650lb-ft from a Z06, the tube twists a -fraction- of a degree, and a small fraction at that.

Originally Posted by 10mm_

Ok I get it now, no wonder my car hooks so good LOL



Still don't take the plate off