Synchrotech B Series Transmission Synchro Master Rebuild Kit

Synchrotech B-Series Synchro Master Rebuild Kit - Carbon or Brass

If your B-series grinds going into a gear, you've probably already adapted to it. You slow the shift down, you baby second, you double clutch without thinking. That's worn synchros, and it doesn't get better on its own. This Synchrotech master kit is the complete fix: synchros for every gear plus the springs, sleeves, bearings, and seals to rebuild it properly while it's apart. Available in brass for a factory-quality rebuild or carbon for a real performance upgrade.

Which Part Do You Actually Need?

Three parts, three different symptoms. Match yours before you spend money.

This kit covers the first two, since it includes both synchros and slider sleeves. If you find worn hubs while you're in there, order those separately, because no synchro kit fixes a worn hub.

How To Tell Your Synchros Are Done

A few reliable signs, and one test worth running.

It grinds into one specific gear. The classic. If everything shifts clean except second, that's second gear'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. If the car upshifts quietly but grinds or refuses on a normal downshift, your synchros are worn.

It's getting worse. 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 transmission fluid. Rule those out first, they're far cheaper to fix than pulling a transmission.

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 over decades, and it costs less. Refreshing a daily driver or a mostly stock B-series, 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 over time. 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 expect dramatically longer life than brass. You're paying for how it engages.

Check Your Hubs Before You Order

The most important advice on this page. 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.

The good news is this kit includes new slider sleeves, so half of that equation is handled. But inspect your hubs and your engagement teeth before you close it up. Sharp and clean means this kit transforms the shift. Rounded off means you need hubs too, and finding that out now is far better than after everything's back together.

What's In The Kit

• 1-5 synchros (carbon or brass, your choice)
• 1-5 synchro springs
• Brass reverse synchro and spring
• 1-5 slider sleeves
• 5 shaft bearings
• 2 axle seals
• Input seal
• Shift rod seal
• New dust boot

That's a genuinely complete rebuild rather than a partial one. Everything that wears in there is covered, including the seals and the dust boot most kits leave you to source separately.

Pick Your Transmission, Not Your Car

Read this carefully, because B-series transmissions vary considerably and the kits aren't interchangeable. Go by the transmission code on your case rather than by what the car is, especially on a swapped chassis where the gearbox may not be original to it.

Three Things That Catch People Out

GS-R and Type R take a different kit than GS, LS, and RS, even within the same 1994-2001 range, because the transmissions are different.

Cable versus hydro matters. Know which actuation your gearbox uses before ordering, since several of these split on exactly that.

The 1989-1991 Integra takes two different kits depending on whether you've got a Y1/S1 or a Y2/A1/J1. Same years, same car, different transmissions. Check the code on your case rather than guessing.

Worth Doing Once

Getting into a B-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 by a wide margin. So while it's open, inspect everything and replace what's genuinely 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 B-series has started grinding and who's ready to fix it properly rather than driving around it. Refreshing a high-mileage transmission, building a gearbox during a swap, or upgrading a car that gets shifted hard. Check your transmission code carefully, inspect your hubs, pick brass or carbon based on how you actually drive, and get your shifts back.

Fits: Honda and Acura B-series transmissions, see the table above. Materials: brass (OEM-style) or Synchrotech Pro Series carbon composite. Includes: 1-5 synchros and springs, brass reverse synchro and spring, 1-5 slider sleeves, 5 shaft bearings, 2 axle seals, input seal, shift rod seal, and dust boot. Important: select by transmission code, not by vehicle.