My ET4 has 11,000+ miles. I had a reason to open the transmission. I believe it is a same transmission as in LX150. I thought I will share some pictures. The pictures are so much clear to see than drawings in owner's manual.

Step 1 - Drain hub oil, remove muffler, rear tire, rear brake drum, etc.

Step 1- Following owner's manual remove 7 screws with an allen wrench.

Step 2 - Two halves of transmission will separate.

Some things I learned are:
1- A hub can take a lot more oil than the maximum as indicated on a dip stick (object #4 in picture).

2- Gear #1 will come off if a nut is let loose on the other side (nut holding clutch axle to transmission cover). Gear #2 easily comes off. Gear #3 comes off with a firm pressure.

3 - I don't know how but some dirt and sand got into my transmission (there should be a small filter). I used a carburator cleaner to clean these off.

4 - Owner's manual recommends using a new gasket (#5) when putting together a transmission. Well my gasket looked fine, so I just reused the old one, and it didn't leak afterwards when I added hub oil, so....

5- I didn't try removing the bearings. According to owner's manual one needs a bearing extractor. Not sure whether these can be removed without an extractor. The three bearings looked identical.

6 - When putting together my bike, I used a little grease between wheel axle, washer, and rear wheel and my rear wheel now rotates much more freely.

7- Use some antiseize lubricant on the 7 screws that hold two halves of transmission casing together.