Honda K24A2 Rear Main Seal 91214-RNB-A01

Genuine Honda Rear Main Seal (91214-RNB-A01) - K20 / K24 & More

The rear main seal sits between the back of the crankshaft and the transmission bellhousing, and it's one of the most common oil leak sources on a high-mileage K20 or K24. This is the genuine Honda part, the exact seal Honda installs at the factory, same rubber compound, same 80x98x10mm dimensions, same fitment tolerance. On a seal that's buried behind the transmission, you want the one that's right the first time, not an aftermarket guess on lip hardness or diameter.

Do It While The Transmission's Out

This is the whole strategy with a rear main seal, and it's why most people are here.

The seal is only accessible with the transmission removed, which means getting to it is the entire labor cost of the job. So you replace it whenever the transmission is already out, a clutch swap, a rebuild, any major bottom-end work. The seal itself is cheap; pulling the transmission is not. Doing them together means you're not dropping the trans a second time to chase a leak that develops from an aging seal you left in place.

If you're doing a clutch on a high-mileage K-series and skip the rear main seal, that's the shortcut that comes back to bite you, the old seal weeps a few months later and you're back under the car pulling the transmission to replace a part you could have done the first time for a few dollars.

Why Genuine Matters On A Seal

On a seal, the rubber compound and spring tension have to match the crankshaft journal spec exactly, or it doesn't seal and you've done the whole job for nothing. The genuine Honda seal is made to that spec, correct lip hardness, correct diameter, correct spring tension, so it seals properly and lasts. A cheap aftermarket seal that's slightly off on any of those can leak from the start or fail early, which on a part this labor-intensive to reach is the worst place to cut a corner.

Chasing A Crank Oil Leak

If you've got oil appearing between the engine and transmission, pooling at the bottom of the bellhousing, or showing up after a clutch job, a failed rear main seal is a prime suspect. It's one of the classic high-mileage K-series leaks. Replacing it with the genuine seal is the fix, and since you're pulling the transmission to do it anyway, it's the moment to handle anything else back there while you're in.

Fitment

K20, K24, and a wide range of other Honda and Acura engines (see full fitment list). Part number 91214-RNB-A01, 80x98x10mm. Genuine Honda, direct factory replacement.

Who Should Grab This

This is for anyone doing a clutch, a rebuild, or any transmission-out work on a K-series who wants to replace the rear main seal while it's accessible, and for anyone chasing an oil leak at the back of the engine. Genuine Honda, correct spec, and a direct replacement. Do it with the transmission out, do it once, and don't pull the trans again for a seal you could have done today.

Fits: K20, K24, and a wide range of Honda/Acura engines (see fitment list). Part number: 91214-RNB-A01. Dimensions: 80x98x10mm. Type: genuine Honda rear main seal, direct factory replacement. Recommended: replace any time the transmission or engine is out.