Honda K20Z3/K24Z7 Mainshaft Needle Bearing 91103-RAS-003

Honda K20Z3/K24Z7 Mainshaft Needle Bearing - 91103-RAS-003

Rebuilding your Civic Si or TSX transmission and you need the mainshaft needle bearing? Honda part number 91103-RAS-003 is the OEM bearing that supports your mainshaft inside the trans case. It's a 35x41x24mm needle bearing that sits between the mainshaft and the case. When you're doing a transmission rebuild, you're pulling this bearing out and pressing a fresh one in. Worn bearings make whining noises and cause mainshaft slop, which screws up your gear engagement. Fresh bearing fixes the noise and keeps your mainshaft centered so your gears mesh right.

Here's What This Bearing Does

Your mainshaft spins inside your trans case while your countershaft drives power through the gears. The mainshaft's gotta spin freely without binding or wobbling around. This needle bearing supports the mainshaft and keeps it centered. Needle bearings use tiny rollers instead of balls, so you get more load capacity in less space. When the bearing wears out (usually after 150k+ miles or running the trans low on fluid), the rollers wear down and you get slop. You'll hear whining in certain gears and your shifts get notchy because the shafts aren't lined up anymore. New bearing fixes it.

Why These Bearings Wear Out

Transmission bearings die from high mileage, low fluid, or contaminated fluid. If you've been grinding gears or you haven't changed your trans fluid in 100k miles, metal shavings from your synchros get in the fluid and wear the bearing down like sandpaper. Eventually the rollers wear and the bearing starts making noise. If you're already tearing your transmission apart for a rebuild, replace this bearing. It's $30. Trying to save $30 by reusing a worn bearing is stupid when you're already $500 deep in labor. Bearings that fail after you button everything up mean you're pulling the trans again.

You're Splitting the Case for This

You can't get to this bearing without fully tearing your transmission down. Trans out of the car, case split, gears and shafts pulled, then you're pressing the old bearing out and pressing the new one in. You need a bearing press or a bearing driver and a big hammer. If you're doing this, you're already doing a full rebuild. Don't reuse the old bearing if it's making any noise or if it's got play. It'll only get worse and trash your fresh fluid with metal particles.

OEM or Nothing

This is genuine Honda OEM. Aftermarket transmission bearings are garbage half the time. Some work fine, some fail in 20k miles. Honda OEM bearings are rated for 200k+ miles. You're already spending money and time on a full trans rebuild. Spending an extra $20 for OEM instead of some $10 Chinese bearing that'll fail is just common sense.

What You Get

• Honda OEM mainshaft needle bearing (part number 91103-RAS-003)
• 35mm ID x 41mm OD x 24mm width
• Needle roller bearing (high load capacity)
• Supports mainshaft in trans case
• Same bearing your trans came with from the factory

Fits Your Car

• 2013-2015 Acura ILX
• 2008-2014 Acura TSX
• 2007-2015 Honda Civic Si

Compatible Transmissions

• K20Z3
• K24Z3
• K24Z7

Note: You need a press or bearing driver to install this. Don't hammer it in crooked or you'll trash the bearing. Press it straight until it's flush. When you're putting your trans back together, use fresh Honda MTF and replace any worn synchros or bearings. Check your case bore before you press the new bearing in. If the bore's worn oval from the old bearing spinning, the new one won't fit tight and it'll spin too. Rare, but it happens on really beat transmissions.