December 11, 2023

Hemmings Fox Body Rehab Eps. 3

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Hemmings Fox Body Rehab Episode 3: Shifted

Tara Hurlin


After a full mechanical inspection and the successful installation of a ProCharger supercharger kit on the 1991 Ford Foxbody Mustang’s 5.0-liter V8, the Hemmings team switches gears to tackle the Mustang’s Achilles heel, the Ford AOD transmission. What better way to get the full benefit of the street car’s 306 horsepower and 334 pound-feet of torque than to ensure that the transmission will send power to the rear wheels reliably and efficiently?

Where most automatic transmissions will let you manually shift through the gears, the Ford AOD transmission will not allow its first gear position to be held. Thankfully, there’s a solution, but it requires pulling the transmission. The installation and use of a manual valve body will allow us to not only shift into any gear we select, but more importantly, hold it until we’re ready to shift out of it manually.

Why keep the automatic transmission instead of swapping it for a five-speed? An automatic transmission is arguably the best transmission for drag racing. For starters, we will be able to avoid the downtime associated with pressing the clutch to switch gears, improving reaction time at the tree. But first thing’s first: before pulling the transmission, we did a little test fitting of our new wheels and big Mickey Thompson tires. It’s a good thing we have Junior Nevison and his problem-solving skills along for the ride.

Searching for a Fox body Mustang of your own? See what’s available on Hemmings.

The Fox Body Rehab series is made possible by:


Classic Industries

Covercraft Industries


Mickey Thompson Tires & Wheels

Moser Engineering

Procharger Superchargers

Race Star Wheels

Summit Racing

U.S. Radiator