Heres the tools you’ll need:
Flip the H22 transmission over in a bin or oil catch container with the bell housing down. This will let the transmission oil to leak out through the axle hole. In this position you’ll see a round plug with a square hole where your ½ ratchet fits. Place the rachet into the square hole and turn counterclockwise to loosen and remove. After removing the plug you’ll see the countershaft bearing and C-clip that locks the countershaft into place. Sit the transmission back down to its rightful position. By having the transmission back flat the rest of the oil will leak out the hole by the C-clip.
Loosen the 3 10mm bolts on the shift mechanism and use a flat head to pry it off. There is a 14mm bolt next to the shift mechanism, remove it. The transmission should be empty by now. Place the transmission on a table or floor with a cardboard or towel underneath. Roll the transmission back onto it bell housing and remove the 12 12mm bolts that runs around the entire case. You will see 2 12mm bolts on the bottom of the transmission, remove them carefully. There is a spring and ball inside each hole.
Once the 12mm bolts, springs, and balls have been removed next step is opening the c-clip and removing the case. Place the needle nose plier into the open end of the c-clip. Open the needle nose pliers and place the Flathead in a gap between both cases. Push down on the Flathead and pry the case up, while holding the c-clip open. Now you should have a gap, place the 2nd Flathead in the gap nearest to the opposite side of the first Flathead. The c-clip should be stuck in the open position and you can now push down on both Flatheads to pop the case off. If you hear a click, that means the c-clip have closed and you will need to reopen it.
Now that the case is off you can see the main shaft, countershaft, 3 shift forks, reverse idle gear, and differential. Over by the reverse idle gear is the reverse mechanism. There 2 10mm bolts holding it down. Remove them and place both the mechanism and reverse idle gear to the side. Place both of your hands around the shift forks, main and countershaft. Pull all together upward to remove them from the case.
To remove the gears from the main shaft, turn the shaft upside down with the clutch side pointing up. All the gears will slide right off. To remove the gears from the countershaft you will have to remove the 19mm nut, that’s on top. Then flip the shaft upside down and bang it on a thick book or wood. It will slowly work its way lo0se.
The last thing left is the diff aka differential. Place the case upright, grab a Flathead and rubber mallet. Place the Flathead in the hole for the axle and tap the lip of the differential gently until it falls out on the other side of the case.
Now let’s put this bad boy back together. Before we can put the transmission back together, the old silicone will have to be cleaned off the cases. Use a small piece of sandpaper and go over the edge of the case where both halves of the case meet. When there is no visible silicone left use the brake cleaner and clean out the inside of the transmission. Let the transmission sit for 10-15 mins to dry.
After the cases is dried we can now install the Diff. Place the Diff in its seat over the axle hole. It should fall in half way down, using the rubber mallet, tap the Diff on the outer edge by the ring gear in a crisscross pattern till it seat flush. Flip case over to make sure the Diff is flush against the case.
With the gears installed back onto the counter and main shaft. Make sure the countershaft 19mm nut is tightened. And the dimple on the nut is pushed back down to lock it in place on the shaft. Place both main and countershaft side by side interlocking. The shift forks must be placed in the correct position.
The small fork is for the 1st and 2nd gears sleeve on the countershaft. The medium fork goes on the 3rd and 4th gear sleeve on the main shaft. The last fork, which is the tallest will go on the 5th and reverse gear sleeve on the top of the main shaft. Don’t forget to put the 2 spacers back on the main shaft bearing in the case.
When holding the 2 spacers together there should be a small gap in the middle. If not flip the small one around. The small one will go on the bottom touching the bearing. With all the forks, spacers, and shafts in position, grab them all together in both hands. Place them into the holes they came out of. Everything will fall right into place.
Next is to put the reverse mechanism and reverse idle gear back. Don’t over tighten the 2 10mm bolts. They should be torqued to about 18lbs. Add silicone to the edge of the case where both cases come in contact. A nice even film of silicone is needed, don’t over do it with the silicone. Also, you only need silicone on the case with the gears.
Make sure that all the shift forks are in the neutral position. This is by placing the shift forks sleeves in the middle between the gears synchros. On top of the main shaft, you’ll see the reverse stopper spacer. At the end of the spacer is a downward L shaped lip. Spin this lip towards the hole for the top bolt on the case.
Place the other case on top the gear set and wiggle it down till the c-clip almost touch the countershaft bearing. Use the needle nose pliers and open the c-clip then push the case all the way down, while holding the c-clip open. The c-clip should be on the bearing in the open position. Place a Flathead under the washer that is under the 19mm nut and it pries up. This we help the c-clip to fall into place and close.
Close to the end now. Place the 12 12mm bolts back and tighten. Place the 2 12mm bolts that had the springs and balls back and tighten. Place the transmission down to its rightful position. Now you can install the 14mm reverse bolt and shift mechanism with the 3 10mm.
You are now finished!