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StangSource.com Tech Center » Tech Articles & How-To's » Project: Kill Thumper

Text and photos by Sean Simpson

love to drag race, plain and simple. After several frustrating trips to the strip it was time to do something drastic to solve the wheel-hop problem caused by the Cobra IRS. Rather than dump a bundle in fortifying my '99 Cobra's Independent Rear

Suspension to handle drag strip duty, I opted to replace it with a solid axle better suited for my needs. The easiest way to achieve my goal was to find someone with a GT that wanted my IRS for its ride & handling and to do a direct swap. I did not do this the easy way.... Being that I was going from scratch, I made the decision that I would try to use the best parts I could afford to save from fixing things later. After locating an 8.8" housing, beefy axles, shocks, and other misc. parts to make the ABS system happy, it was time to decide on suspension parts. I never really

considered any other supplier than UPR Products. I've worked with Jeremy and the crew at UPR on many occasions and their suspension parts are quite well known and respected among many NMRA racers. After explaining my intended use for the car, Jeremy recommended their adjustable upper control arms and non-adjustable lowers with urethane bushings as well as a rear stud girdle cover to beef up the stock 8.8" housing.

After collecting a pile of needed parts, the swap was under way. It was fairly straight forward with the exception of the ABS wires and a few brackets. The IRS was reverse engineered to fit these cars so all the required mounting points for the solid axle were already in place. I

took my time and did a little detail work while everything was apart, no sense in hurrying now and doing a half-way job. Two evenings and a few skinned knuckles later the job was complete! After the first test drive all of my apprehensions about ride quality were put to rest, it truly felt like a different car and the ride was fine. The car feels much firmer and better suited for my needs. I should have done this long ago....

Now for the true test, the local 1/8th mile drag strip where I had cursed the IRS so many times before. It was time to put the new solid axle and UPR's "Pro-Street" suspension parts to the test. My previous best with the IRS was a lazy wheel-hopping 8.87 second E.T. with a 2.2 second 60 ft. time. After getting used to the right amount of clutch slip to keep the DR's happy on the very green track I pulled a much improved 60 ft time of 1.8 seconds and managed an 8.29 second E.T.! Anything you can do to knock more than a half second off your E.T. is well worth it, I had a smile from ear to ear!

I'd like to take this opportunity to thank those who helped me with the swap and give a special thanks to Jeremy and the guys at UPR Products for their top notch suspension parts that made this project possible.

Check 'em out!