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I have an 88 CRX Si that I'm restoring and swapping a D15Z1 into. The engine swap and wire conversion are no problem for me, but I thought I'd also like to mix and match the gears between the two transmissions. I want the Si 1-3 with the VX 4-5 and final. I don't have any transmission experience prior to this and I'm on a time constraint as I plan to move out of state some time this month (this project has been ongoing since before I decided to move).

My concern is the Si 3rd gear and the VX 4th gear. I read that the 3-4 shift fork isn't interchangeable between these two transmissions. The CRX uses PL3 forks and the VX trans has PL3 for 1-2 and 4-5 but a P20 for 3-4.

Here's my question: Can I use the CRX's shift forks to go from the CRX 3rd to the VX 4th? Or the VX's?


Here is the setup:

1998 CRX Si
case
mainshaft
countershaft
differential
1st-3rd gears
reverse shift fork
clutch disc

1992 Civic VX
ring gear
4th-5th gears
flywheel

I've got the hybrid cable trans all mock assembled, it just needs to be cleaned up and lubricated before I put it all back together. I'd like to know what fork to use so I can just clean everything up and put it together in one shot. If I have to try both sets of shift forks, I'll get everything dirty again (and also waste my limited time).

Thanks

Also I'm curious if it would have worked with mixed up 4th and 5th main and counter gears. It all seemed to mesh up and spin correctly, then I went through and counted teeth for confirmation and realized I had accidentally put the VX 4 and 5 counter gears with the Si 4 and 5 mains. (4 was with 4 and 5 was with 5) That would have given me gearing between the Si and VX's, but would it have blown up?

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If anyone is interested, the CRX is fully stock and complete, in great shape except for seat wear and rusted body panels. The underside, suspension, and exhaust are all surprisingly rust-free.

I made my own plug n play OBD1 VX adapter harness to plug the Z1 engine harness into the CRX strut tower plugs. Additional wires that had no OBD0 analog were ran directly to the ECU to splice into the OBD0 to OBD1 harness so that the CRX wiring and Z1 engine harness are completely untouched. Then I trimmed up a MAP sensor bracket from a donor CRX to mount the VX's EGR controller to on the firewall. The adapter plugs were all cut from donor cars, mostly an 88 Legend.

The idea is that I could pull out the D15Z1 and drop the original engine, harness, ECU back in, then put the Z1 into another car without having to repair any wiring. Just pull all my adapter wiring out.

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I tried both and they both fit just fine. What would cause the 3-4 fork to be incompatible if the diameters are the same?