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Old 03-09-2020, 10:48 AM   #4
Scooby Specialist
Member#: 239822
Join Date: Mar 2010
Chapter/Region: South East
Location: America's Penis
2010 WRX


There's some good info here:

How does this compare to the stock WRX gears? Subaru has increased the strength of the standard gears used in the USDM WRX models over the years so it really depends on the model year used for comparison. The Type STi and Type RA gear sets are factory based gearset options that we pieced together into a complete kit and improved on with the REMŽ superfinishing process. When we first introduced these kits the 2002 WRX was the current model and these sets were a fairly substantial improvement for the weak standard gearbox. As the years progressed the strength difference became progressively less. With the introduction of the Legacy GT gearbox and later the MY2008 WRX (which had the same gears as the Legacy GT) the primary difference between the Type STI and the factory gears became simply the superfinishing process.

In terms of specific numbers the percentage increase in strength looks approximately like this for MY2002 WRX vs. Type STI/RA based on tooth size and surface treatment benefits: 1st = 15-20% increase, 2nd = 33-38% increase, 3rd = 42-47% increase for RA / 28-33% increase for STI, 4th = 5-10%, 5th = 5-10% although sometimes in extreme cases 5th gear will fail by splitting from the base of the tooth to the inside diameter of the gear and the RA gear has much greater material thickness here. In comparing MY2003 to MY2007 WRX the difference in 1st, 2nd, and 3rd is reduced noticeably becoming: 1st = 10-15% increase, 2nd = 17-22% increase, 3rd = 35-40% increase for RA / 15-20% increase for STI. In comparing MY2008+ WRX the difference becomes only the surface treatment which we estimate somewhere in the 5 to 10% range. The only exception being that the RA 3rd gear will provide an additional 10% due to its larger tooth pitch.
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