Synchrotech F/H Series Transmission Synchro Master Rebuild Kit

Synchrotech F-Series & H-Series Synchro Master Rebuild Kit - Carbon or Brass

If your Prelude or Accord grinds going into a gear, the synchros are worn and it isn't improving on its own. This Synchrotech master kit is the complete fix: synchros for every forward gear plus the springs, sleeves, bearings, and seals to rebuild it properly while the case is open. 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. 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. 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 than pulling a transmission.

Accord Owners: Measure Your 3-4 Fork

This is the most important section on the page, so don't skip it.

The two Accord kits are separated by 3-4 shift fork thickness, not by transmission code. That matters because six transmission codes (P2A5, P2U5, M2L5, M2S4, M2J4, and M2J5) appear on both kits. Reading the code off your case will not tell you which one you need.

6.5mm fork takes SYN115-3A, the 1992-1995 kit.
7.5mm fork takes SYN115-3, the 1996-2002 kit.

They're not interchangeable. A 6.5mm fork car will not accept the 7.5mm kit and vice versa. Measure it rather than guessing from the year, especially on a car that's been swapped or rebuilt over the last thirty years.

And Check Your Second Gear Synchro Design

One more thing while you're in there, and this one catches people.

Both Accord kits are built for a 3-piece dual cone second gear synchro. Some early models came with a single piece second synchro instead, and those won't work with either kit.

So verify your second synchro design before ordering. If you're not certain what you're looking at, get in touch and we'll help you identify it. Better a phone call now than the wrong parts with the transmission already apart.

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 car, 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, or have built the engine, this is the one.

Straight talk: 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

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 one.

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 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, including the seals and dust boot most kits leave you to source separately.

Find Your Kit

Both Accord kits require a 3-piece dual cone second gear synchro.

Worth Doing Once

Getting into the 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.

Who Should Run This Kit

This is for the Prelude or Accord owner whose transmission has started grinding and who's ready to fix it properly rather than driving around it. These cars are twenty-five to thirty-five years old now and the synchros in them have done a lot of shifting. Measure your fork if you're in an Accord, verify your second synchro design, inspect your hubs, and get your shifts back.

Fits: 1993-2001 Honda Prelude, 1992-2002 Honda Accord, 1998-2001 Accord Euro R. See the table above for the correct kit. Materials: brass (OEM-style) or Synchrotech Pro Series carbon composite. Includes: 1-5 synchros, springs, and slider sleeves, brass reverse synchro and spring, 5 shaft bearings, 2 axle seals, input seal, shift rod seal, and dust boot. Important: Accord kits are determined by 3-4 fork thickness, not transmission code, and require a 3-piece dual cone second synchro.