How I opened my B series Honda transmission.

B series transmission open

Set the Transmission on a pair of wood 2×4. This keeps the clutch shaft from hitting the ground.

Y21 transmission

Next, you will want to loosen the bolt on top. This covers a snap ring holding a bearing to the case half.
Remove bolt from transmission

Just use a 1/2″ wrench.
Unbolting transmission bolt

Here is the view inside.
Clip holding bearing on trans shaft

Next, to loosen a lot of bolts…
removing bolts to open trans case

Here is a view of one side.
some of the bolts to remove

Now all those bolts are removed.
more bolts to remove

Remove the bolts on the side of the housing. And remove the reverse button (this button turns on/off your reverse lights).
bolts with springs and bearings, reverse button

There are little springs and ball bearings inside. be careful not to loose anything.

Now remove the bolt from the other side.
another bolt to remove

Now get your snap ring pliers out.
snap ring pliers

Here is an animated GIF image I made to show you how to click the snap ring out of place.
gif image of using snap ring pliers on y21 transmission


You may need a rubber hammer to gently tap the case loose. be careful, you do not want to crack the aluminum.
rubber hammer to tap case lightly

You can also fit a small pry bar in a few places to get the case a bit loose. but be careful not to chip or crack the case.
Prybar to prop up case loose

Here is another place the pry bar works.
alternative prop location for pry bar

After a few minutes shaking, prying, and moving it around, I got it open!
opened up b series transmission

Don’t forget while your in the transmission to clean the magnet!!!

Magnets removed from transmission case
Magnets removed from transmission case (Just pry it up and it pops out)
Another view where the magnet is at.
The dirty magnets! filled with metal shavings!
Now they are clean, and ready to reinstall. They just push right back in place


This was the 3rd time I had to open my transmission case.

1- Bought the car with a bad clutch, opened to inspect.
2- Rebuild with carbon synchros, new bearings, and changed 5th gear to LS gear.
3- Metal plate on freeway was pulled up into my transmission housing, causing a leak.

I used my Honda factory service manual to accomplish this job. Its a great resource for anyone working on their car.
It covers every step in good detail, and has lots of diagrams and information about everything on the car.
I highly recommend you get the manual and use my website to help visually.
Honda service manual page on b series transmission popout diagram

I bought the manual for the 1994 Civic Del Sol because I have a Japanese b16 with USDM del sol smog parts and a y21 transmission.
Service manual 1994 Honda civic del sol Vol 1 and 2