I'm going to replace my manual transmission. What else should I replace at the same time?

Question

Vehicle
2006 Civic Si
115k miles
6-speed manual transmission (original, including clutch)

Question
It's getting harder to shift between gears. When upshifting, I need to wait a while for revs to match perfectly in order for the shifter to fall into place, and when I'm at the track it can be tough to rev-match well enough to shift quickly. I assume the synchros are worn.

Looks like I'll need to replace the transmission before too long. What's the general recommendation for what should be replaced while I'm in there? I expect that much will just depend on visual inspection, and I'm wondering about what to look for as well. Specifically, what about:

• Clutch
• Flywheel
• Other clutch parts (slave cylinder, release bearing, release fork, etc.)

Answer 1

From the mileage and your description I would replace the clutch no matter what if you swap out the transmission. But, before replacing the transmission, verify the clutch pushes the release fork enough, and/or try flushing the clutch master cylinder and lines.

Because a clutch that won't release fully gives the same symptoms as worn synchros.

If you do replace the transmission:

• Resurface or replace the flywheel, clutch, throw-out bearing.
• Like cano said, replace the rear main.

Answer 2

Might as well change the trans fluid and possibly the rear main seal while your there. But you pretty much have everything.