Muscle Mustangs & Fast Fords
5R55S Transmission Rebuild - Taking It To The Next Level
Level 10 rebuilds a 5R55S after years of abuse behind a supercharged ’06 Mustang GT
Level 10 addresses a third issue regarding line pressure that is controlled by the electronic solenoid. According to Barrett, there are 30 (computer written) lines of programming for line pressure and transmission functions in tuning software like the SCT products he uses. He said not every tuner modifies the trans functions properly. The solenoid is cranked up manually to eliminate any tuner problems. Level 10 raises the line pressure from 90 psi to 180 for proper operation in high-performance applications.
The final issue is the Overdrive and Intermediate servo bores in the case. The factory case is made from a weak aluminum, states Barrett. He went on to tell us that the bores become distorted and leak fluid past the servos. The servos control the line pressure for the Intermediate and Overdrive bands inside the transmission. It makes tuning the line pressure inconsistent, since there is no way to accurately know what effect the servo leakage has on it. Because of this, the servo bores are modified and an insert is installed to prevent the distortion. This will make the servo actuation consistent and predictable so the transmission tune can be properly adjusted.
On top of those modifications, Level 10 added the usual upgraded parts, like better clutches and bands, and it does an overall inspection of the major components. Once completed, the 5R55S was ready for a long service life on the street and strip.
Giagnacovo is ruthless on the car as two of the three NMRA events he attends each year are far from his home state of New Jersey. It brings reliability to a whole new level when you drive your race car to the races. His routine includes tossing his luggage and a pair of Mickey Thompson drag radials (mounted on stock Bullitt wheels) in the trunk and hitting the road. Its best time (11.24 at 120 mph) came last year when Giagnacovo drove the Stang to Bradenton, Florida, for the NMRA Spring Break Shootout, where he competed in the JDM Super Stang category. The Florida race is nearly 20 hours from his home, yet he didn’t think twice about making the journey sans truck and trailer.
JDM Engineering re-installed the transmission and Giagnacovo is happy to report it shifts nicely, and the new Level 10 torque converter (approximately 2,600-rpm stall speed) is barely noticeable on the street, but is effective when he jumps on the loud pedal. The final test came in March, when he drove from New Jersey to Bradenton, Florida, to compete in the NMRA season opener. Although he lost early, the vehicle ran strong and withstood the racing, as well as the 1,500-mile trip.
Filling Up the 5R55S
Level 10 recommends Mercon 5 fluid only, and the transmission takes 9.5 quarts. Barrett warns that the transmission is sensitive to the fluid level. A special fill tube (available from Snap-On, Matco, and others) screws into the transmission pan, and a hand pump like the one shown is required. Barrett recommends pumping in six quarts before starting the vehicle. Once the six quarts are in, start up the engine, run the shifter through each gear, put it into Neutral, and pump in the remainder of the fluid. There is no dipstick on these transmissions. You’ll know when it’s full when you pull out the fill tube and the pan just drips a little bit of oil, notes Barrett. He finished with one more tipfill the transmission when the fluid is 180 degrees. If filled cold, then fluid will push out of the vent.