2015 Chevy Corvette Z06: Overheating Issue. Is It the 8-Speed Transmission’s Fault?

2016 chevy corvette z06
Chevy Corvette Z06

TFLcar recently received a report of a 2015 Chevy Corvette Z06 coupe overheating after one fast lap at the Pueblo Motorsports Park near Pueblo, Colorado.

Michael Pettiford of Go4It Services stated: “I took a 2015 Corvette Z06 coupe with the 8-speed automatic for a fast lap around the Pueblo racetrack. The coolant temperature went from around 220F to 260F after one lap and I had to bring the car back in.” When asked about the ambient temperature, Michael said; “It was a late morning and temperature was around 80F.” Michael added, “The Z06 showed a high level of grip. The braking performance was excellent, and the cockpit ergonomics were outstanding.”


TFLcar reached out to Chevrolet for comment and quickly received a response. Chevrolet communications referenced a recent blog post by Tadge Juechter, Corvette chief engineer.

The complete blog post is copied verbatim below. The summary of the statement is that the C7 Corvette Z06 was designed and tested to run competitive racing laps for an indefinite amount of time when equipped with the 7-speed manual transmission. This is tested and verified with the ambient temperature of 86F (or 30C).

The Z06 equipped with the 8-speed automatic transmission puts a higher demand on the engine due to closely spaced gear ratios and higher average rpms. The post also states that the Z06 with an Automatic is capable of faster lap times when compared to the Manual.

Here is the blog post by Tadge Juechter in its entirety.

There are lots of interesting back stories behind recent media tests, but the question asks about Road Atlanta so for the purposes of this thread I will focus on our long lead media event last November.  We spent a week there with journalists from around the world.  We had pro drivers Tommy Milner, Randy Pobst, and Andy Pilgrim behind the wheel along with many other very capable drivers.  They were permitted to run consecutive laps with minimal or no traffic, so essentially “qualifying laps”.  Over the course of the week we had 2 cars come into the pits with a hot warning messages.  The first was due to the loss of an accessory drive belt.  We had a pre-production tensioner on that car which failed, throwing the belt and we lost the water pump.  We have had no issues with production tensioners.  The second car was an automatic.  I believe it was being driven by Randy on the hottest day there which was right around our design performance target of 86 degrees (more on that below).  After multiple laps at speed he came in with a hot warning message.  Although the car had been out on track all week, that was the first and only incident.  In Corvette’s 60 year history, we have never put automatics on track for media and never encouraged people interested in track usage to buy automatics.  The new 8 speed automatic gives us a chance to put more automatic transmission customers on the track.  Since there is some lack of clarity around the true capability of each of the transmissions, this question gives us the opportunity to publish some guidelines:

•The Z06 Manual is designed to keep engine oil, coolant, transmission and differential fluids below the hot warning targets when driven by a professional on a 30C day (86F) on a “typical” racetrack for an indefinite period of time (effectively the time to burn through a full tank of fuel).  Our team validates the durability of the Z06 cooling systems with a 24hr accumulated track test to simulate a full season of amateur racing or aggressive track-day usage in these conditions.

•We designate our track: the Milford Road Course, as the “typical” standard, but recognize that there are tracks around the world which are easier on a cooling system and some which are harder on a cooling system.  Generally speaking, tighter tracks with lower average speed and higher sustained RPM, will drive higher fluid system temperatures.

•Higher temperature ambient conditions affects all car’s abilities to run sustained laps at ten-tenths.

•The Z06 Automatic transmission put in “Drive” selects the lowest possible gear ratio for best acceleration, and because it has 8 closely-spaced ratios typically runs higher average RPM than the manual.  This optimizes lap time performance, but also taxes the engine oil and coolant more for any given track.  So the automatic has the capability to run faster laps than the manual, but thermal limitations are reached more quickly.  Customers who are planning to run extended track-day sessions at ‘professional’ speeds, are advised to go with the manual transmission, or to paddle shift the automatic and select higher gears when conditions warrant it.

•Any time the maximum recommended temperatures are reached in any condition, the DIC will give warnings at the appropriate time for coolant, oil, or transmission fluid.  A cool-down lap or two will bring operating temperatures back to a reasonable level and aggressive track driving can be resumed.

Some may wonder why don’t we design to higher temperatures, say 110 degrees to accommodate southern tracks in the Summer.  We have used the “pro driver at 86 degrees” criteria for generations of Corvettes and for the vast majority of customers, it has resulted in excellent performance for their usage.  If we designed to higher temperature criteria, we would have to add a lot of cooling hardware which drives mass up and perhaps more importantly, you have to feed the system with more air which has a huge impact on appearance and aerodynamic drag.  Like most aspects of car design, the challenge is in finding the best balance of conflicting requirements.

Learn all the details about the Corvette Z06 convertible here.

Watch the Corvette Z06 coupe debut at the Detroit Auto Show.