S197 Mustang T-3650 5th Gear

VIR Testing- March 2015

We brought our 2006 Mustang to VIR for the first time in March for a post winter shakedown. The car got a long winter's rest and standard maintenance- rebuilt dampers, new suspension hardware, several new bushings, and a new helmet blower/fresh air intake system. Some continual weight reduction in several miscellaneous areas also got the car weight down to 3,295lbs with fluids, no driver.

However, our primary takeaway from the weekend was our gearing issue.

We learned that the gears we have been running all of last year (the 3.73's) are not ideal for this long track. The stock mustang transmission has a .62 5th gear overdrive that takes 1.1 seconds to engage, which at 125mph translated into a an amazing 194feet of coasting! The drag of the car lowers the speed by 2.3MPH, when then takes 2.5 seconds and 453 feet to regain the speed lost due to the shift. While I still contend it's possible the lower gears make for a better run out of some of the corners, i think it's outweighed by the extra shifting. 

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While our quickest time was a 2:11.2, it seems that Mike Skeen in a Spec Iron car has been able to set a 2:08.2. I think that with some more practice, fresh tires, grippy track conditions, and a 3.31 gearset we might have be able to get close.