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Some notes from a k20 6speed transmission refurbishment, this car was made in 2002, it is now the end of 2025. We pulled this apart so we can install a Cusco LSD into the unit. While this is removed I intend to replace whatever is ruined.

Before pulling this out, I had noticed some notchyness when shifting between 1st->2nd, as well as the 3rd gear popping out of gear when on track. So I wanted to take a look at the internals to see if there was any wear.

Fresh out of the car. grime

I prefer washing down as I work, it makes the assembly more fun. washed

You can see the shaft in the background has 1/2 and 3/4 gear sets. Note the lack of wear on the syncros. internals

This to me looks acceptable… close-up

So what gives? Why the notch? I know it’s there I’m not imagining it…

I have another theory, that the wear on the motor mounts is actually causing this issue. Three of the four mounts are shot, in my eyes this could introduce enough force into the linkage/forks to where the gear can pop itself out. Same thing when you feel the notch between 1st and 2nd. Its the shift of the drivetrain that is causing the instability.

The cost of maintenance I suppose, it’s still not too bad.

So whats next?

  1. order parts (always the first thing to do…)
  2. drop off the flywheel at the machine shop for a resurface.
  3. Setup clutches in LSD
  4. install the LSD and measure the thrust washer clearance.
  5. order OEM parts from japan (thrust washers, motor mounts, various seals)
  6. order transmission fluid? Motul?
  7. Reassembly of Gearbox.
  8. Subframe refurbishment.
  9. Reinstallation.