So im in need of some help im swapping a F23A1 into my 1991 Honda CRX Si so far im pretty stuck on what manual transmission i need i know about the M2B4 but damn
they are pretty short in the gears i really need a transmission that will be somewhere around 2.5k rmp at 70-80 MPH this info would be GREATLY appreciated I know H series transmissions will work on the Fseries but so far ive only been finding the low gear ones. i need longer gears since i want to daily this and not be screaming at 70 MPH on the freeway. so if anyone knows of any F series or H series transmission the will bolt onto my F23A1 with gears long enough to be at like 2.5k rpm at 70-80mph that would be creamy
(ALSO i dont really want to swap my hubs but i can if need be so if any info on axles that will fit that trans and my chassis in length that would be cool.)

 

You're gonna be hard pressed to find a transmission that will put you at 2.5k rpm for 70-80mph with the smaller tires you'll be running on your CRX. Any H/F series FWD transmission will bolt up to your F23. They all share the same bellhousing. Just steer clear of the H2A5 transmission out of the 90-93 Accords as they have a generation specific bolt pattern for the mount that will not line up with your swap mounts. H22 trans will be the shortest and F22 will be the longest. F22 gears are extremely long for what they are. An H23A1 trans will be a decent middle ground. 5th is not too short and 1-4 give good acceleration on the F series.

Click this. You can get a better idea of transmission ratios and the end results here.

 

That was the one transmission I was looking at, how did you get this info about the H2A5? What's the big difference?

 

And yeah 2.5K is a bit much to ask for, I'd be happy with 3.5k at 75

 

I bought one years ago and found out the hard way. It has the 90-93 trans mount bolt pattern and can't be changed. It's literally only that transmission for whatever reason. Every other H/F manual transmission has 2 additional holes so that the studs for the mount can be moved to accept either bolt pattern.

 

High RPM is not bad for cruising. With most Honda engines you'll get better fuel economy than you would cruising at a low RPM.

 

I agree. I cruise around 4k @ 80mph with my F20B/M2S4 and get ~30mpg highway.

 

Everything has been leading towards the m2S4, the reason for me isn't so much of fuel economy more so reliability and I don't want to wear my engine rod bearing down faster, and by bolt pattern do you mean for the tranny mount rear and passenger or do you mean to the mating holes to the block

 

The passenger side mount is what I've been talking about. If you look at where the mount bolts to the trans, there will be 3 studs for the mount. 95% of all the H/F trans also have two additional holes down there so that you can swap the studs around for either mount pattern, depending on your vehicle. The H2A5 was a very early F series trans and lacked the extra holes to move the studs. It would be best to stay away from that trans regardless because the gear ratios are incredibly long.

The M2S4 is a great fit for the SOHC engines. The H23A1 engine it was designed for only revved to 6500rpm anyway so it's very close to the SOHC F series. It drops you perfectly back into the powerband on each shift. Here's a video of my old F22B1 setup with the M2S4 trans to give you an idea of the powerband.

 

I'll give it a try I'm just worried about all the complaints for that trans always breaking and having weak synchros, thank for the advice

 

You won't wear the engine bearings.

There are no Honda synchros that are stronger or weaker than another.

Transmissions break when they aren't maintained properly, are abused, or aren't built to handle the power running through them.

 

I've never heard anything related to an H/F series transmission being weaker than any other and I've been doing this a long time. I put 450whp through a 300k mile M2S4 and it's still going strong in the car today even though the engine is long gone....

 

Well that aspires some hope for my build, not having to search high and low for a trans thank you

 

I know this tread is old but will the H series axles fit my 91 crx hubs or will I have to get Integra hubs? If so what's all needed?