B20A JDM B2K5/F2K5 Taller 5th Gear Options For Freeway Driving

Hello, I have been lurking here quietly for a few years and this is my first post on any Forum. (There is a wealth of information on this Forum but I cannot find the answer to my question listed in the title). I have just installed a 1986 Gold Top B20A into my 1986 LXI and am surprised at the ~4000+ Engine RPM at highway speeds vs the ~3200 RPM of the original LXI Engine. From what I can tell, my best option for a taller gear set would be to install a 5th gear set from a F22A1/A4 MT with transmission codes: (MPT3, H2U5, M2L5). These transmissions can be found on 4th gen Accords/Some lower trim Preludes and have a 5th gear ratio of .685-.705 with a final drive of 4.062. The B20A B2K5/F2K5 has a 5th gear ratio of .794 with a FD of 4.066 & the LXI A20A3 5th gear is .694 with a FD of 4.066. The reason why I believe the 5th gear sets from these transmissions could fit my B2K5 is they share the same main-shaft needle bearing size of 38X43X26mm 91104-PG1-771 / 91104-P21-008. But I have not been able to confirm if the main and counter shafts have the same spacing so the gear sets will mesh correctly or if the spline count is the same on the countershaft gears. No other Honda/Acura transmissions seem to use the 23XXX-PF5-XXX series gears except for the 3rd Gen USDM Preludes which also have fairly short gearing so I cannot tell though matching P/Ns and deductive reasoning if the gear sets will fit.

Has anyone successfully changed the gear sets (especially 5th) on the B2K5/F2K5 JDM B20A Engines? Would like to know what you have found before I start buying gears/used transmissions and removing/opening up my transmission.

Hello and welcome to the forums.

I dont think I every heard any one doing what your trying but I think its a great idea.

A million years ago and guy named Mr. bone or Mistabone used to do Honda transmissions like that. He was on hondahybrid.org and I think Honda tech. If you can search him out I think he could tell you if it can be done.

I have not heard this being done on our tranny's but this is a common thing with other Honda tranny's. Lots of internal parts being interchangeable.

This might be a better question on preludepower, we really only know much about the a20 trans