4-cyl transmission compatability question

[Volones]

It looks like I'll be replacing, or rebuilding, my transmission soon and I have a couple of questions.

Can I replace my F-series with either an F5M-R from a '90-'92 protege (B8-ME engine), or an F25M-R from a '92-'94 protege (B8-ME engine)?

I want the 3.619 final drive ratio instead of the 4.105 that my current transmission has. All the internal gear ratios are the same, and my desire is to have the engine spin at closer to 2,500rpm at 70mph rather than 3,000+rpm at 70mph.

Does anyone know if the bolt pattern to the engine is the same on the B8-ME and the B6-DE? Also will my current axles and speedometer cable work? Has this been done before? I tried searching and spent all morning reading about the V-6 transmissions, swaps and automatic transmissions, but couldn't fine any info to answer my question.

Thanks for your time,
Vol!

[Volones]

OK, so I found GroHarlem's guide to engine swaps and it had some great info about the different transmissions (Thanks Gro!). Then I went to a protege transmission info website I found and got some more info on gear ratios and other things. Then I called around and found a salvage yard that has both the original tranny from my '95RS and one from a '91 protege 1.8L SOHC (B8 engine), and I'm going to go take a look at them and see if the bolt pattern matches. If it does then I'll get that tranny and proceed with a swap. My desire is to improve my mileage by running at a lower RPM (but still within the powerband of my little engine) at the same highway speed.

I'll update here, or start a worklog if that would be better. It prolly won't have any pics though.

Vol

[MX_Sid]

hey man that sounds great! i just6 blew out my fifth gear and can't decide if i wanna rebuild with a bigger gear like a mx-6 if it fits but if you find a whole better tranny keep posting the worklog thing sounds good. do we got the same engine? '92rs

[Volones]

Hey,
I just replied to your post. I have a '95RS, so I have the DOHC. I honestly don't know if the bolt pattern is the same as the SOHC. I believe the bottom end of our engines is the same, so that makes me think they use the same transmission.

Vol

[Volones]

So, I took a little trip to the salvage yard at lunch, and the F5M-R transmission from a '91 protege 1.8L SOHC will not bolt up directly to the 1.6L DOHC MX-3 engine. However, it looks like I can swap the bell housing from my F25M-R transmission to the F5M-R and it should fit perfectly. If that doesn't work (and I'm over 90% sure it will), I can swap the differential from the F5M-R to the F25M-R and get the final drive ratio that I want. I plan on making a worklog when I do this and posting it up with pics so others can use this info. My desire is to get better fuel economy, and since I'll be driving 350+ miles each way to get to where I'll be doing the work, I should have some preliminary mileage numbers to report after I finish the replacement.

Vol