C5 Corvette With A 4L80E Transmission - First C5 4L80E Conversion

For those of you who remember Mike Romaine from our 9-10 second power adder track shootout (April '07), you may recall that this New Jersey-based '99 FRC C5 ran quite detuned at our shootout, on just straight 93-octane pump gas, and still managed 9.70s-an easy four tenths off his previous best (of 9.33). At the time, his IRS-equipped remote mounted single turbo setup easily owned quite a number of Internet "fastest" titles, running nines with three different combinations (nitrous, n/a and turbocharged). Next he had his sights on running 8s, so first he switched to a 402 motor combo with TEA-ported TFS 235cc heads, and had Cartek modify the custom STS remote mount turbo setup for a larger air-to-air intercooler and 88mm T6 turbo. The good folks at Mufflex did the pipe bending for the project.

Unfortunately, though, even with RPM Transmissions' stoutly built 4L60E, Mike had no shot at fully ringing out this combo and breaking into the 8s. It was time to step up, as many C5 owners begrudgingly did before him, and retrofit a Turbo 400 or a Powerglide. To Mike's distaste, this would mean many side effects he wasn't prepared to deal with ... keep in mind he not only drives his C5 to and from the track, but also puts a good amount of street miles on it otherwise (about 7,000 per year). Thankfully Mike and RPM Transmissions came up with an alternative solution-retrofitting the baddest electronically controlled transmission GM ever made: the 4L80E.

Step one, RPM put together its Level V 4L80E with a Vette-style output shaft, good for over 1,200-rwhp (or at least they think since no one has actually broken one yet), and Stage 3 C5 differential using 300M axles and a turbo-friendly 3.42 gear. That was the easy part, something RPM had done hundreds of times before. Step two was finding out how to mount the differential, trans and torque tube. After machining off the 4L80E's large bell housing, an RPM-fabricated billet adapter plate was used to form a union with a small Vette-style bell housing, and another custom billet adapter plate was used to mate the trans to the rear along with a complementing brace. To compensate for the 4L80E's added length the torque tube had to be shortened, re-centered and welded. Custom prop shafts from The Driveshaft Shop then took home in the shrunken torque tube. Step three, the legendary (and late) Leo Barnaby of Carroll's Rod and Racecraft had to clearance the floorpan for the new trans' increased girth, which essentially meant cutting a couple huge pieces out with a plasma cutter (where the torque tube meets the converter and bellhousing)-then replacing it with some fresh sheet metal.

Mike was gracious enough to send these pictures along of the build to show you how it was done. With RPM's Level V 4L80E, Mike managed to shatter his old times by almost a full second with an 8.87 at 155mph. All thanks to his new 402ci motor and turbo, and the trans that could hold it. Romaine says he is still dialing in the combo, which has still not bested his previous 1.36 short time despite a new electronic trans brake. With an added 300-lbs (for a total of over 3,700lbs with the 300-lb driver) from the new roll cage, larger turbo, intercooler, piping and heavier trans-that very well might not happen. Another note, due to some issues with his meth kit, Mike has been using Sunoco 100 to run 8s, and produce 1,007-rwhp and 980 lb-ft of torque. Though he says, with a new meth kit, or modifications to the current, he may very well be going back to running 93 octane with methanol injection again. Yeehaw!

Sources

RPM Transmissions
800-406-1109
www.rpmtransmissions.com
Cartek Racing
www.cartek.net
Neverlift Racecraft
www.neverliftracecraft.com

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Check out the first C5 Chevrolet Corvette with a 4L80E transmission swap.
Jul 1, 2009

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