My transmission is acting up, doesn't know which gear to stay in and doesn't yield much torque from the engine.
I'm replacing it, what transmissions should I look into, the engine is the JDM black top H23a from the 92-95 Prelude Si, and the car is 1990 Accord.
something I'm looking for in the transmission is good highway fuel economy if I can choose to.

 

I believe the best for gas mileage would be the m2s4.

I'm copying from another post someone made about this:

f22a1 trans ( m2L5 ) .. longer gears and fuel economy, also good for Turbo - stays in gear longer taking full advantage of Boost. .. But .. Too slow of a transmission for All-Motor setups.

h23a1 trans ( m2s4 ) .. happy median between short gears of the h22 trans the the long gears of the f22a1 trans. A popular all around transmission.

h22a1 trans ( m2f4 ) .. the usdm trans that was equipped in '93-'96 Prelude VTECs. A short-geared transmission that is Great for an All-Motor setup, quick acceleration, does not loss VTEC between shifts, .. But .. fuel economy on this trans Sucks !

hope this helps.

 

I think you're info is accurate, but it looks like the OP is looking for an auto trans based on the title.

OP stop me if you are in fact planning to do a manual swap, but the original auto trans for your accord is going to be the best for highway mileage. I suggest finding the root cause of the drivability issues before spending a bunch of money, but a rebuilt stock trans may be the best option based on your description.

 

If your current transmission is the stock one, I would recommend staying with a similar unit. 90-91 Accords had sport shift and had some differences with the transmission/wiring/and TCM that would make swapping in a different transmission more difficult. Find a used one if you're willing to take a risk or get a rebuilt unit as suggested above.

 

I apologize, I *was* in my head presuming a manual for some reason.

So.... I would also say stick with stock original auto transmission type.