This is an update and not been tested by me
I have been pondering the question of how to take a "Craigslist" transmission and convert it to EV use without a lot of money. It was a challenge but I believe I have the answer. Several of these mods have been done by me at different times and on different transmissions, and one in particular is a new one for me. While I believe this will work, I take no responsibility if you want to try it.
1. If you find a decent powerglide, or any other automatic transmission these mods should work on all except the later electronic ones. (these instructions are for a powerglide)
2. Locate the pressure port for low gear band apply and install a hydraulic flow control valve there. like this:
Drill and tap a hole in the transmission case or pan (at least 1/4" NPT), run a hose from the valve to the new oil return port. Open the valve fully as a starting position. Drive the car and close the valve a bit at a time until the car takes off like you want it to.(softly as throttle is applied). Like an automatic clutch.....
3. Clean out the pan and install a new filter while you are there.
4. Buy a direct drive coupler and the correct flange from Speedway Motors. Their drive has a removable and adjustable flange while other kits do not. They have flanges for early and late Chevy engines. You need to get the special snap ring with it too. (About $150-$175)
5. Do not put a hose to the modulator, leave it alone and the transmission will run in high pressure mode.
6. The last mod is a little trickier. The modulator presses or pulls a rod in and out to regulate the shift point RPM. if left alone, your transmission will only shift up at very high RPM's. (I can only guess at 4,500 or so)
Each car built, each driver, every terrain and traffic condition-has their own
best shift point. You can alter this point by unscrewing the modulator and pulling out the little push rod that sets the pressure and shortening it a little.
It would take several tries to get it close to what you need and you would need to drain and refill the pan each time......
OR remove the modulator completely and make a replacement fitting with a screw adjustor so you can do this easily and quickly.
And like the hydraulic valve setting, once set, you will probably not need to move it again, but you would have that option.
All of these mods should give you a 2 speed transmission that needs no external pump. You should have either an automatic or manual shift. And it would be adjustable for an easy or abrupt take off, an adjustable RPM for the shift point and doable for under $500 if you watch and are careful. All without having to disassemble the transmission if it was decent to start with.
The only down side: You have turned the low gear brake band into a clutch and it will wear faster than normal, but the lighter weight the vehicle, the longer it will last. If it ever gives trouble, you will always have high gear and will not be stranded. I would recommend you install a Kevlar racing band
in the beginning if you can, they are tough as hell....