3rd Drive Gear TY856 6MT Ratio 1.521

3rd drive gear for 6-speed manual transmissions with trans ID codes starting with "TY856".  This is one of the two taller (longer) 3rd gear ratios used by Subaru for USDM STI MY07-18, Legacy Spec B, and Forester STI.  It is also used in our RST-F145Kit (2nd-6th long ratio) gear set with REM.

Optional REM ISF© (superfinishing) treatment.  ISF is a precisely controlled treatment that reduces surface roughness left from the machining processes thereby improving reliability, reducing friction, and all but eliminating break-in requirements and the resulting swarf.  Ideally, we recommend treating both contacting gears (drive & driven sides) for optimal results.  Adding ISF processing may increase ship time by as much as a week.

Gears may need to be replaced due to gear tooth failure or damage to synchronizer dog teeth.  The peaks of the synchro dog teeth should be sharp and without any noticeable burrs.  Damaged synchro dog teeth due to gear clash or missed shifts will reduce the shift performance and severe damage can cause gear lockout or prevent gear disengagement.

Other possible sources of gear failure are overheating due to lack of oil supply, damage to bearing race surface resulting from bearing failure, or thrust surface wear due to heavy loading and/or lack of lubrication.

Gear Ratio: 1.521

Tooth Count: 23

Manufacturer Part Nos:

• 32275AA560 (USDM STI MY07-18, Forester STI) ... 4 hole gear type - MY01-06 requires updating synchronizer.
  
• 32275AA590 (Legacy Spec B)