I have found a few amazing teardown and rebuild guides for Honda Transmissions, the best one being a S20 guide that is image heavy on another forum.
Does anybody know where I could find one for a S40 B000 transmission for a D16Y8? I have never opened up a transmissions before but I feel confident in my ability to repair it if I have a strong tutorial. I also want a comprehensive list of the tools required to rebuild the S40 so I can weigh doing it myself vs having a local transmission shop do the repair. It looks like the most expensive thing I would require is a hydraulic press which amazon.com has for $111 with free shipping.
Any and all info is appreciated, as well as telling me why I'm an idiot for wanting to try to tackle this alone. Once I actually get down to it if I do it myself I will create my own thread with lots of photos and tips.

 

Helms manual.

 

Scrap the press. Use that money to purchase a Helms manual and a 3-prong bearing puller.

 

I'd say the same. Actually as far as pulling the bearings on the gear stacks I just use a big block of hardwood and turn the input and countershafts upside down and bring the ends down on the hardwood a couple of times and they slide right off.

 

Helms manual

Except for the K series I also use the block of wood to disassemble the shafts.

 

Helms manual it is. Putting this project on hold temporarily since a guy at a transmission shop is 99% sure my popping out of 2nd gear is related to my shifter being broken. The bushings have completely rotted away so there is nothing between the metal on both sides of the linkage, and the bottom of the shifter is so rusted I don't know how it's hanging on. I have ridiculous play and he thinks I am not fully engaging 2nd gear. So ordered a Skunk2 and Energy Poly Bushings, wish me luck.

 

If it's engaging the other gears fine i'd say it's more likely the countershaft bearing walked. I think every Y8 i've pulled apart now has had that bearing walk out. If you open the transmission and find out it has, tap it back in and stake it in there so it doesn't happen again.

 

Got the dual-bend skunk2 shifter installed, and polyurethane bushings on the linkage, holy crap what an improvement over stock! No play whatsoever, I use to be able to move it a full 3inches in either direction WHILE in gear.

Anyways, this is mostly resolved the popping out of 2nd gear issues. It will still do it if I'm just coasting around and decelerating in 2nd, but accelerating and normal driving it hasn't popped out once. So basically it only does it now if I try to. I probably still have a bearing walking out, but it's now driveable until it gets worse.