IAG Spec PPG 1st - 4th Straight-Cut Synchro Gear Set for 2004-21 Subaru STI

The IAG-Spec PPG Straight-Cut 1-4 Synchro Gear Set is designed for weekend racers (and weekday racers for that matter) who prefer the streetability of a synchronized gearbox which is suitable for daily driving. The kit features strong, straight-cut gears (vs. traditional helical gears) which provide maximum performance and durability for high horsepower Subarus and can be safely driven on the street.

Straight Cut For Extra Strength

The OEM gear shown on the left is cut in a "Helical" Style. Notice that the shape of the teeth are designed to wrap around the gear. Helical gears are used in most OEM transmissions due to their quiet operation and easy engagement. The teeth are much thinner and weaker than the IAG PPG gear on the right with "Straight-Cut" teeth due to the helical style.

Eliminate Extra Shifts

Our engineers worked directly with PPG to specify custom gear ratios which allowed us to increase top-speed in 1st and 4th gear. This change will prevent extra shifts while drag racing. Additionally, the gearset is designed to utilize the OEM 5th and 6th gears for quiet highway operation and maximize streetability.

While the synchronizers improve drivability for the street, the taller 1st and 4th gears are the stars of the show when it comes to racing and all-out acceleration. A 1st Gear Ratio of 3.077 results in an 8-10 mph increase vs. OEM (years vary) while the new 4th Gear Ratio of 1.042 will ensure that you finish out your quarter mile pass without shifting to 5th.

* Chart reflects a 9000 RPM redline with a 26" tire. Speeds are shown in MPH.