Our Boosted Three-Valve Made Too Much Power!


If you’ve followed our 2005 Mustang GT build, then you know that we’re slowly but surely transforming our S197 Three-Valve Mustang into a 10-second street/strip machine with the help of our friends at UPR ProductsQA1Race Star IndustriesMickey Thompson Tires & WheelsSteeda AutosportsSPEC ClutchBrisk RacingBrenspeedSCTHurst Performance and Vortech Superchargers thus far.

Just last week, we detailed in a separate story the installation of our Paxton NOVI 2200SL supercharger kit, which brought power into the low 400s at the rear wheels thanks to our newfound boost. Thinking we had all of our bases covered with our new twin-disc clutch assembly and a one-piece aluminum driveshaft and safety loop, we assumed an arsenal of wheels, tires and suspension would be enough to propel us down the drag strip more than a handful of times. At least, that’s what we thought…


“Sucks to suck,” as the saying goes, and it sure as heck does. On the first pass out at our local drag strip — Auto Club Dragway in Fontana, California — our completely stock TR-3650 five-speed manual transmission gracefully met its maker.

We say gracefully because it left silently without even a whisper. On that initial pass, we brought our 28×11.50-15LT Mickey Thompson ET Street R bias-ply drag slicks up to temp, set to around 19 psi. It was our first time out to the strip with our new combination, and our heart rates were up.


We dropped the hammer at 3,000 rpm on the launch thanks to an MSD Performance two-step that a friend (and hot shoe on this pass) let us borrow. With our QA1/UPR double-adjustable suspension not even dialed in for the first pass, we spun all the way through first gear to a measly 1.9 60-foot. If you’ll recall, this car still has the factory 3.55 gears in the rearend, so even with the larger 28-inch bias ply tires, our effective gear ratio is still hovering around the 3.40-3.42 mark.

Shiting like a mad man toward the eighth mile, clocking in at 8.8 at more than 80 mph, our driver realized we had lost all of our gears. As we coasted to a 13.4 at 108 mph, we knew something in the car wasn’t happy, and weren’t happy with our results. While we haven’t torn down the transmission, we suspect the factory 10-spline input shaft snapped right off.


If you’re not familiar with the shortcomings of the factory five-speed manual transmission in the early S197s, there are essentially two main weaknesses – a remote-style shifter and a 10-spline input shaft. Owners of the 2005-2010 Mustang GT will be more than familiar with these issues, and it’s not uncommon for enthusiasts to snap this input shaft after bolting on upgrades like a more aggressive clutch, a set of slicks and more than 200 horsepower from a blower.

It’s safe to say, we’re currently in the process of sourcing a Tremec T56 Magnum XL six-speed manual transmission as a one-and-done solution for our street/strip daily, so keep an eye out for that in the near future as we bring you the full installation details.

About the author

Harrison Noble

Living in San Diego for most of his life, Harrison was exposed to a variety of cars at an early age. His passion for anything that is fast, or has a V8, brought him to Power Automedia.
Read My Articles

Blue Oval Muscle in your inbox.

Build your own custom newsletter with the content you love from FordMuscle, directly to your inbox, absolutely FREE!

Free WordPress Themes