dblair

I picked up an M2Y4 with plans to rebuild and do a couple up grades. Taking my time with it as I have an M2A4 currently in the car and it's still working well.

The .812 5th gear is a bit shorter than the.787 (I think) in the M2A4 so I'm thinking about changing it. I remembered some discussions about this so I searched and discovered that at least some of the F series transmissions have 5th gears that are thicker than the one in the M2Y4 and need to be machined.

Can anyone tell me which transmissions have 5th gear sets that will just drop into the M2Y4? I'm planning on buying the gears new so something from a USDM would make things easier.
The .787 doesn't seem excessively tall so something around .750 or so might be worth a try.
The low gears in the M2A4, especially 1st, seem a bit on the short side which is why (along with availability and price!) I decided to go with the M2Y4.

dblair

So.....nobody knows, or did I not write the question so it makes sense?

v4lu3s

i havent looked at all that in years, but if i recall correctly there is no direct drop in interchange between f and h series transmissions, i think you had to do some milling and stuff to make it work, but its been over 5 years and my memory is very rusty.

dblair

Do you know if all the H's are interchangeable?

holmesnmanny

I'm sure synchrotech transmissions people would know this.

apexi_bb6

I have a gearset for a 92 si (Cant remember trans code off the top of my head) and I bought a fifth gear set for a 98 spec us F23a1 from majestic Honda for about $100 shipped and it fits just like factory on the input and output shafts, visually they are the same thickness, but I can try to Mic them out today for reference. I have a good 2.3 si trans Im going to swap the gears into in the next week or so, just havent had the time for it.

Here's the thread I based this project off of.

https://honda-tech.com/forums/honda-accord-1990-2002-2/f23-5th-gear-into-h23-transmission-2411948/

dblair

Thanks Apexi, that's the kind of information I'm looking for. Don't know how I missed that thread.

Haven't torn into my M2Y4 yet, anyone have pics of a 5th gearset from one?

apexi_bb6

This is a pic of them side by side (si gearset left vs accord gearset on right)

dblair

I'm assuming the "Si" is an H23 correct? It's probably the same as an H22 box, but can you confirm?

apexi_bb6

I cant, both my spare internals and my spare trans are from h23 transmissions. I will pull apart my 5g h22 trans eventually but thats several months down the road.

Ran the numbers and the h23 5th is 0.8125, and the f23 is 0.6857

dblair

That's where I am as well. I don't plan to tear the M2Y4 down til I have a plan and am ready to proceed. Thanks to you when I do I'll at least be able to compare the gears to the pics and get a good idea if they're compatible.