Honda K20A2/K24A2/K20Z Mainshaft Brake Arm 24412-PNS-000

Honda K20A2/K24A2/K20Z Mainshaft Brake Arm - 24412-PNS-000

Rebuilding your RSX Type S, TSX, or Civic Si transmission and you need the mainshaft brake arm? Part number 24412-PNS-000. This is the arm that stops your mainshaft from spinning when you shift into reverse. It sits under your gear selector shift arm inside the interlock assembly. When you slam it into reverse, this arm engages and brakes the mainshaft so reverse gear can mesh without grinding. Without it or if it's worn, you're grinding gears every time you go into reverse.

Here's What This Arm Actually Does

Your transmission's mainshaft is spinning whenever you're in gear moving forward. When you shift to reverse, the mainshaft's still spinning from momentum. If you try to engage reverse while it's spinning, the gears clash and you get that horrible grinding noise. The mainshaft brake arm fixes this. When you move the shifter to reverse, the brake arm engages and physically stops the mainshaft from spinning. Once it's stopped, reverse gear can mesh cleanly without grinding. It's a mechanical brake inside your transmission specifically for reverse gear. If the arm's worn or broken, there's nothing stopping your mainshaft and you're grinding into reverse every time.

Common Failure on High-Mileage Transmissions

The mainshaft brake arm wears out over time from constant use. Every time you shift to reverse, it's engaging and stopping a spinning shaft. After 150k+ miles or aggressive driving, the arm wears down or the contact surface gets smooth. It can't grip the mainshaft properly anymore. You start getting grinding going into reverse even when you're stopped. It gets worse over time. If you're already rebuilding your transmission and your reverse gear's been grinding, check this arm. If it's worn or damaged, replace it. Don't put a fresh transmission back together with a worn brake arm and have reverse grinding again in 10k miles.

Installs Inside the Interlock Assembly

The mainshaft brake arm sits under the gear selector shift arm inside the interlock. You're not getting to this without splitting your transmission case. If you're doing a full transmission rebuild, you're already in there. Check the arm for wear. If it's worn smooth or cracked, replace it. If you're just doing a clutch job and you're not opening the trans, you're not touching this part. But if you're rebuilding internals, inspect it and replace it if needed.

What You Get

• Honda OEM mainshaft brake arm (part number 24412-PNS-000)
• Stops mainshaft rotation when shifting to reverse
• Installs under gear selector shift arm in interlock assembly
• Prevents reverse gear grinding
• Same arm your transmission came with from the factory

Fits Your Car

• 2002-2006 Acura RSX Type S
• 2004-2014 Acura TSX
• 2006-2011 Honda Civic Si

Compatible Transmissions

• K20A2 6-speed (2002-2004 RSX Type S)
• K20Z1 6-speed (2005-2006 RSX Type S)
• K20Z3 6-speed (2006-2011 Civic Si FA5/FG2)
• K24A2 6-speed (2004-2008 TSX)

Note: This arm's buried inside your transmission within the gear selector assembly. You're not getting to it without splitting the case. If you're doing a transmission rebuild and you've been grinding into reverse, inspect this arm closely. Look for wear on the contact surface where it brakes the mainshaft. If it's worn smooth or there's any cracks or damage, replace it. When you're installing it, make sure it moves freely and engages properly when you move the shift selector to reverse. If it's binding or not engaging all the way, something's not right. Fix it before you button up the case. Testing your shift mechanism with the case open saves you from pulling the trans again later because reverse is grinding.