The science behind Corvette C7 Stingray and upcoming 2015 Corvette C7 Z06 torque tube failures

As the massive and very premature Corvette Stingray torque tube failures continue, the same unavoidable fate waits for the upcoming 2015 Corvette C7 Z06.  Why?  Because apparently neither +Tadge Juechter or anyone on his fine Corvette engineering team or in the entire +General Motors has absolutely no knowledge of physics, especially the aspect involving thermodynamics and material science.


This is a truly shameful situation, a single reason sufficient to dismiss Juechter from his chief engineer duties and there are so many other reasons already.


What is happening with the newest Corvette is a very sad testimony to the condition of our high school and college education.  How could someone with absolutely no knowledge of physics earn an engineering degree?  Did Tadge and the rest of his team earn their degrees from Manila and Tijuana universities?


There is only one saving grace that keeps Corvette C7 sales going, the equivalent if not greater ignorance of the newest Corvette buyers.  Generally speaking, intelligent, educated and science savvy buyers are a very seldom exception among the Corvette owning crowd.  Even now, when more and more of them line up at their local dealership service lines, rubbing elbows with big crowds invited there by Recall Mary, they absolutely have no clue why they are there, complaining about noises coming from their torque tubes, after accumulating few thousand or even just few hundred miles on their precious new acquisitions.


Have the buyer had any knowledge of physics, thermodynamics and material science, they would never even consider buying the newest Corvette but since they did, they deserve exactly what is happening to them.  Certainly, one cannot claim being educated by reading GM sales brochures and listening to their sales persons or +Tadge Juechter alone.  If they do, this is exactly what happens...


First of all, the mode of failure:  carrier bearings failing due to lack of lubrication and thus, the rattle.


Torque tube carrier bearings are a wear item, without any doubt but their lifespan should fall within 100-150 or even more THOUSANDS of miles, not 2 or 3 thousand miles or even less.


What is the cause of lack of lubrication?  A very simple answer here: bearings are subjected to extended periods of high temperatures, with the torque tube acting as a frying pan (this should be simplified enough for even a Corvette buyer to understand?)


Where is the heat coming from?  Of course it comes from the engine and most of all, exhaust system.


Someone ignorant may point out that two previous generations of Corvette had exactly the same layout and experienced no premature carrier bearings at all.  Exactly the same set up?  Well, not exactly.


There are two major difference between past torque tube set ups and the newest one.


1. The center tunnel plate is now located below the exhaust instead of being sandwiched between the torque tube and exhaust.  Yes, the plate is perforated and there are heat shield measures but dealing with the effect instead of avoiding the cause is never ever as effective (Tadge does not understand this part at all).


2.  The torque tube housing is now made of STEEL instead of ALUMINUM.  A measure taken to (again) deal with the EFFECTS of AFM induced drivetrain vibration. 


When combined, these two reasons create a very firm assurance that all of the seventh generation torque tubes will not only failed but will continue to fail periodically.


What is exactly the real problem?  The answer lies in PHYSICS, and specifically in FOURIER's LAW.


Here is the scientific explanation and exact cause of carrier bearings failure:


Fourier's law states that the rate of conductive heat transfer is proportional to the transfer coefficient and the temperature gradient of the material(s):

q = k * ∇T

Aluminum has a much higher conduction coefficient (k) value than steel, therefor the amount of heat transferred from the exhaust and engine will be greater given the same ∇T.


BUT....

 Aluminum also has a much greater specific heat (Cv) than steel does. The first law of thermodynamics states;

ΔQ = Mass * Cv * ΔT

This means that for the same amount of heat transferred (Q) from the exhaust, the aluminum will have a lower temperature. This means that while the car is shut off and exhaust is cooling, the aluminum block will have a larger ∇T than the steel, thereby having a higher rate of heat transfer as you can see from Fourier's law. 

To put it simply once again, the aluminum torque tube housing will never get as hot as its steel counterpart and it will cool off considerably faster as well. 

Now, the question is, why doesn't Tadge or any other GM engineer understand this part? 

How does this affect the upcoming Corvette C7 Z06?  After all, Tadge and GM marketing advertise this car as one with "carbon fiber driveshaft, thus unaffected by the Stingray heat and cooked carrier bearing issues?

As usual, Juechter speaks half truth only.  Technically speaking he is correct, the actual driveshaft INSIDE of the tube is made of carbon fiber to reduce the rotational inertia BUT...

THE HOUSING IS STILL THE SAME STEEL  AS BEFORE.  Since the carrier bearings are mounted in the same steel housing, they will cook as much as they do on base car.

As usual, with Corvette buyers, nothing beats learning the hard way or more specifically, not learning at all since once kool aid drinking GM sheep, always the same sheep.