Synchrotech Bearing & Seal Synchro Rebuild Kit for K Series

Synchrotech Bearing & Seal Synchro Rebuild Kit - Carbon or Brass

If your transmission grinds but everything still stays in gear, this is the kit you want. It covers the parts that wear out and cause bad shifts, synchros, springs, bearings, and seals, without the sleeves you're paying for in a master kit and may not need. Available in brass for a factory-quality rebuild or Synchrotech carbon for a real performance upgrade.

Do You Need Sleeves? Start Here.

This is the only meaningful difference between this kit and our master kit, so figure it out before you order. Three parts, three symptoms:

If your only complaint is grinding, this kit handles it. If a gear also kicks itself back out under throttle, that's a sleeve problem and you want the master rebuild kit instead, which includes them. And if you find worn hubs while you're in there, order those separately, because no synchro kit fixes a worn hub.

What A Synchro Actually Does

Worth understanding, because it explains why the fix is what it is. Your transmission uses a synchromesh system, and the synchro is the friction ring at the heart of it. When you shift, the gear you're selecting spins at a different speed than the shaft it needs to lock onto. The synchro grabs that gear and drags it to matching speed in a fraction of a second so the teeth mesh cleanly instead of colliding. When that friction surface wears down, the synchromesh can't keep up, and the teeth clash. That's your grind.

How To Tell Yours Are Worn

A few reliable signs, and one test worth running.

It grinds into one specific gear. If everything shifts clean except third, that's third's synchro. Isolated grinding almost always means an isolated problem.

Downshifts are worse than upshifts. This is the useful one. On an upshift, revs are falling naturally and the synchro gets help. On a downshift it has to drag the clutch disc and input shaft up to speed by itself. So if the car upshifts quietly but grinds or refuses on a normal downshift, your synchros are done.

It's getting worse over time. Wear starts as slight notchiness and progresses to metal-on-metal grinding you feel in your hand.

One honest note: grinding can also come from a clutch that isn't fully disengaging or from low or wrong fluid. Rule those out first, they're far cheaper to fix.

Carbon Or Brass?

Both fix a grinding transmission. They suit different cars.

Brass is the OEM-style material and the right pick for most street cars. It restores factory shift feel, it's proven, and it costs less. Refreshing a daily driver, start here.

Carbon is Synchrotech's Pro Series, using a full carbon composite lining built on carbon-carbon technology originally developed for aerospace. The material acts as a braking element during engagement, stopping the gear faster, which means less grind on high-rpm shifts and less wear on your sleeves and engagement teeth. If you shift hard, run track days, drag race, or make real power, this is the one.

Straight talk on one point: carbon shifts better, but don't buy it expecting dramatically longer life than brass. You're paying for how it engages.

Check Your Hubs And Sleeves Anyway

Even though this kit doesn't include sleeves, inspect them while the transmission is open. Synchros work against your hubs and sleeves, and if those surfaces are worn, new synchros of any material won't fix your shifting. New carbon on a chewed-up hub is no better than new brass on a chewed-up hub.

Look at the engagement teeth, the sleeves, and the hubs before you close it up. Sharp and clean means this kit will transform the shift. Rounded off means you need those parts too, and it's far better to find out now than after everything's back together.

What's In The Kit

• Synchros for every gear
• Synchro springs
• Bearings
• Seals

No sleeves, which is what separates this from the master kit. If you need those, the master kit is the better buy than adding them separately.

Pick The Right Variant

Read carefully, because K-series transmissions use different synchro designs and the kits aren't interchangeable. The difference is cone count, meaning how many friction surfaces each synchro uses, and Honda varied it across the lineup and even across model years of the same car. That's why the RSX appears in more than one row.

If you're not certain which design your transmission uses, check the code on the case before ordering. Getting this wrong means parts that won't work in a job that takes real effort to get into.

Worth Doing Once

Getting into a K-series transmission is the expensive part of this job, whether you're paying a shop or spending your own weekend. The parts are the cheap half. So inspect everything while it's open and replace what's actually past spec rather than what you assumed was bad. That's how you close it up once and get the shift you were after.

Who Should Run This Kit

This is for anyone whose transmission grinds but still holds every gear, and for the builder refreshing a gearbox who's already confirmed the sleeves are good. You get everything that actually wears without paying for parts you don't need. Inspect your hubs and sleeves, pick brass or carbon based on how you drive, match your variant carefully, and get your shifts back.

Fits: K20, K24, and L15B transmissions, see the variant table above. Materials: brass (OEM-style) or Synchrotech Pro Series carbon composite. Includes: synchros, springs, bearings, and seals. Does not include: sleeves, see our master rebuild kit if you need those. Important: select the variant matching your exact model, year, and synchro design.