Repairs HR215 5.0 Masters - Transmission slipping - How do I add/change fluid?

OK experts, I'm new here and hope to get some really good advice! My neighbor gave me an old Honda HR215 5.0 Masters lawnmower and it has worked well for a couple of years, but now the transmission is "slipping".

Symptoms:
Start the mower, push both handles the wheels move a little (3 rotations) and then stop. I placed the mower on a block with back wheels in the air, started the mower, drive shaft turning just fine out of engine and into transmission. Push handle to engage transmission and back wheels turn, change gears and speed changes, place hand on wheel with very little resistance - it stops. From what I've read, sounds like I need to replace the fluid, but I cannot locate any bolt or cap that seems to allow access to the case for draining or filling the fluid.

After ALOT of research I'm fairly certain that my transmission is a 20001-VA3-J02 or maybe J04. Below are several links that I "think" are my transmission - sure looks like it!

I have some links to diagrams and pictures but, as a new member I cannot post links.
About the mower:
The attached pictures are all of the information I could find stamped on the mower - there is nothing else - serial number is gone. Hopefully these provide enough information to positively identify the mower, if more pictures might help, just let me know.

I think you may have problem with the ratchet in the wheels you have HR215 k1 SXA with 3 speed gear trans.I have HR215 K1 HXA hydrostatic but it look alike

Hello,

You need to remove the plastic access panel on the mower deck directly behind the engine. There is one small bolt (10mm?), at the bottom of the plastic piece, the top is just held on with plastic tabs that fit into slots in the aluminum deck. You'll see the transmission sitting pretty far back, there should be a black plastic fill cap/dipstick on the top of the transmission. Clean the area of grass clippings (an old tooth brush and 409 work great) before removing cap, use only Honda hydrostatic fluid to top off.

I don't believe there is a drain plug for the transmission.

See the thread I started named "New to me HR173 + HR215 Masters mowers" for a picture of the transmission (same as yours).

Regards

Jeff