3rd/4th Driven Gear Cluster TY856 6MT Ratio 1.521/1.137

3rd/4th driven gear for 6-speed manual transmissions with trans ID codes starting with "TY856".  Early models use a wide keyway (10mm wide) and later models use a narrow keyway (7mm wide).  This is used in our RST-F145Kit (2nd-6th long ratio) gear sets.  We offer an adapter keyway to use a later narrow key gear cluster in a wide key application (available separately on our site) when necessary.  

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 (3rd) / 1.137 (4th)

Tooth Count: 35 / 33

Manufacturer Part No:

• 32254AA600 Narrow Key (USDM STI MY07-18, Forester STI MY07)
  
• 32254AA540 Wide Key (Forester STI MY04-06)