Official Transmission Swap Information (Update 21/05/2010)

[stevesei]

I disassembled the FS gearbox today.It looked very clean and I was able to verify that the gears are as follows:

This is the FS 4-cylinder box. Ratios are:

MX-6 (FS) & 626 (FS) / G(2)5M-R
Gear Ratios
1st 3.307:1
2nd 1.833:1 (45% rpm drop between 1st and 2nd)
3rd 1.233:1 (32% drop) (MX-3 = 1.310:1, 22% drop)
4th 0.914:1 (26% drop) (MX-3 = 1.030:1, 21% drop)
5th 0.717:1 (21% drop) (MX-3 = 0.795:1, 23% drop)
Final 4.105:1

With the stock gears, 3900@80mph, new gears - calculated 3300@80. I think that's worthwhile! BTW, that's a theoretical 145mph top speed if you can pull 6000rpm in 5th.

[crazycanadian]

Here this is a good gear ratio/speed calculator... It can even show rpm drop for each shift... Its a down loaded excel spread sheet... You click the link on the web page..

http://westfield-world.com/gearboxshifts.html

[stevesei]

It's been a while since I posted about the 4cyl 626 transmission I got to transfer into my MX-3 box. Keeping in mind that you can't just swap the 4 cylinder box into a V6 - different bellhousings.

I disassembled the MTX using crazycanadian's very helpful pictures and narrative. I also pulled and disassembled my 92 GS MTX. According to the literature, the MX-3 SHOULD use a G5M, the FS is a G25M. Lo! It appears that the 92 in fact has a G25M, or a severely update G5M. So far as I could tell, the internals are identical, except that the 90K miles FS box had a lot less wear on the synchros and shift assembly. Two easy ways to tell; the 5th gear covers were the same and both boxes had a long plastic oiling trough sticking out into the 5th gear area. Both of these are characteristic of the G25M.

One word of caution: I intended to use the FS taller gears with the GS 4.39 final drive. Without better facilities, that wasn't to be. It requires pulling the bearings off of both shafts, which probably means 4 new bearings. New bearing were not in my budget, so I looked at the idea of using the 4.11 FS final drive. I ended up transferring the entire internal assembly of the FS box to my GS box. I took a chance and reused the bearing shims that came with the FS gearset, after considerable soul searching and a couple of trial assemblies to made sure everything turned and there was no discernible endplay. I got lucky; you may not! Measure the endplay!

Results:
The "new" box is a joy. No noise, no whine, good synchros (90K easy family car miles vs 200K MX-3 sporty driving miles). If you look at my last post here, you see the progressively smaller gaps between gears, which mimics the torque characteristics of internal combustion engines in general. It also shows that in addition to the final drive, 3rd, 4th, and 5th are taller gears in and of themselves. 4th ends up roughly equivalent to the MX-3 5th, and 5th becomes much more a highway gear. The final result is 70mph at about 3000rpm. PLEASE NOTE that this is a great setup for a slightly modified KLDE or ZE. Both are "torque" motors tho the ZE is less so. I think the K8 would pull these gears, but it would be sluggish, to say the least. This setup is also definitely NOT the hot ticket for drag racers, although a turbo car might like the longer gears.

I did this swap hoping for better highway performance while retaining enough gearing for autocrossing. I think it is going to be just right; less wheel spin of the line and in corners, and a 70mph 2nd gear that will pull from about 30mph.

[Josh]

I am so on the fence with doing this!! All the syncros in my new GS trans have been replaced and the entire thing rebuilt. I want to do this gearing swap. I guess if I go to the PnP this weekend and one of the seven 97+ Escorts there has a good trans I will grab it. If not I will just continue with the 626 5th gear swap. decisions decisions...

[crazycanadian]

I am so on the fence with doing this!! All the syncros in my new GS trans have been replaced and the entire thing rebuilt. I want to do this gearing swap. I guess if I go to the PnP this weekend and one of the seven 97+ Escorts there has a good trans I will grab it. If not I will just continue with the 626 5th gear swap. decisions decisions...

I am that little devil on your shoulder Josh.. Just go for it!! do it! do it!...

[wytbishop]

I'm totally going to do it.

[Josh]

Alright I am convinced. Hopefully the syncros are interchangeable between the two gear sets. I am going to the PnP on Sat hopefully I come up with a trans. Only because I think I may boost, whether it be with the ZE or FE...

[RX8SE3P]

Wow I am very impressed with the people swapping to taller gears. I have a 4.10 MX-6 gearbox in my ZE and even that is geared far too short. The KL in the MX-3 hardly needs such sort gearing so it's good to see a good solution has been found. I believe I was at 3300-3500 cruising at 110kmph recently (almost 70 mph). It's just ridiculous if you were to cruise at a higher speed, the engine is making far too much power, it's like you've permanently geared down to overtake. Cruising beyond 120kmph (75mph) at almost 4K is absurd. Plus 1st gear is almost useless at the moment, I can take off in 2nd and probably beat the old K8's acceleration

I have a spare K8 gearbox and I am wondering about doing this swap/messing around with it. From what I gathered, just the gears and final drive are swapped?

Stevesei and crazycanadian - We don't have Escorts here, steve you said you used the final drive and gears from a 4cyl 626? Which year of 626 does this come off? Any other transmissions we can steal a longer gearset off (longer than 4.10)?

[Nd4SpdSe]

Wow I am very impressed with the people swapping to taller gears. I have a 4.10 MX-6 gearbox in my ZE and even that is geared far too short. The KL in the MX-3 hardly needs such sort gearing so it's good to see a good solution has been found. I believe I was at 3300-3500 cruising at 110kmph recently (almost 70 mph). It's just ridiculous if you were to cruise at a higher speed, the engine is making far too much power,

it's like you've permanently geared down to overtake.

I know, I loved it! Was on the K8 trans too, and she was just ready and wanting to go. Just crusing, you can feel it felt like you were just giving it milimeters of throttle, and that's part of where the fuel economy comes in because of these motors needing revs to make the torque, and you need torque to move the car.

Cruising beyond 120kmph (75mph) at almost 4K is absurd

That's typically normal for low torque cars, Japanese especially. My sister's H32 Prelude was, my Mx-3 was and my Rx-8 is like that too.

Before you embark on this mission to change your gearing, I would highly recommend to install a vacuum gauge in your car before hand. You can gauge the engines workload with the gauge and you can see how hard she's working, and you'll be able to compare after you've changed the gearing.

[RogueWolf]

Ryan,

One more transmission with ratios to add to the list...

This one comes straight from Japan care of the Mazda 626 Stationwagon Diesel, or the 323F Diesels.
(Many Japanese importers can get these transmissions)

The Transmission code is a G25M-R, with an ID code of G5M3, or G5M4, the only difference between the two transmissions is the FD. (One is the same as the 1.8V6 MX3, @ 4.388, the other is the same as the MX6 with 4.105) Regardless, the 5th gear is 0.690:1.

So for those of us running @ 4000rpm @ 120km/h on a stock MX3 transmission (0.795:1 5th), this swap will drop that to a comfortable 3500.

Now if you paired that up with the mythical 3.409 Final Drive ratio... You wouldn't break 2800RPM at 120km/h... but your car would not feel all that fast.

I'll let everyone know how my 0.690 swap goes.

[specialtyneed]

Ryan,

I am a bit dislexic so please ignore the typos in my worklog & other newbie posts on the engine code B6-DE 1.6L I4.
Due to popping out of 5th gear in last 2 years and whining (really rattling) sound since bought it. Just read all this thread again. 1st time was about 3 years ago when I got the biggest issues on my neglected '94 RS with ~187k (now 208k) mi, dead disty converted myself to external 2ndary coil w/ post info here, bad clutch, with F25M-R verified by cover plate contour. I have entire paper FSM and PDF '01-'03 trans overhaul with both F25M-R & G25MR data but no oem part numbers.

I want to overhaul a junk yard pull of another F25MR (verified by
1994-01 Sephia 1.8LBK210BK21M5TXM5TX2000-01 Rio (19.25mm Thick Rear Pinion Brg)BK431BK431WSM5TXM5TX2000-01 Rio (22.00mm Thick Rear Pinion Brg) BK431ABK431AWSM5TXM5TX2002-04 RioBK431ABK431AWSM5TX contour and neglected dirty condition never been opened by lack of tool marks on bolts) in my living room in the next couple weeks.
After fruitless searches for parts except input main shaft & output shaft bearings and both shaft seals the only more complete kits I found were for an alternate trans not mentioned here by those #'s on Oreilly's site called M5TX (bearing kit BK277) which is used on:
'91-'94 Ford non-turbo fits all CAP5, TR5B, M5TX
All w/ 24.4mm ID input ball bearing.

Edit: some paydirt on M5TX applications:
Below chart info from http://www.manualtransmissionpart.com/KIA-catalog.html

Year model Eng bearing kit, kit w/syncros

1994-97 Sephia 1.6L BK277A, BK277AWS
1994-01 Sephia 1.8L BK210, BK21
2000-01 Rio (19.25mm Thick Rear Pinion Brg) BK431, BK431WS
2000-01 Rio (22.00mm Thick Rear Pinion Brg) BK431A, BK431
AWS
2002-04 Rio BK431A, BK431AWS.
'89-93 Mazda M5TX

From Amsoil site:
Kia Sephia, also just found out '05 Rio 1.5L is M5TX (per amsoil vin search)
I hope this M5TX transaxle that is setup with 26 tooth output teeth /grooves instead of 28? Or is it a aftmkt earlier gen beefed up franken trans on Orielly' site that is just a tease and you must send your trans out as availability leads that way? Am I missing something?

Above and below from manualtransmissionparts.com which has bearings common to these 2 others CAP5, TR5B. Looking at the kits there are differences in the M5TX but what is it really and why can't I find any sites listing the F25M-R with parts?

Does anyone really know if I can just use the M5TX bearing kit?

BTW, I want to do this carefully and use my salvage trans entirely if within service specs but I know the car pulled from had about 163k mi on it and bearings probably won't be useable after pulling them off even with my impressive array of shade tree tools and very good skills. I can not throw a bunch of dough at this. It's my work car and I feed 6 of us. To make it harder the pull it yourself salvage here has crushed all the compatible vehicles and is pretty sparse lately.

[RX8SE3P]

Wow I am very impressed with the people swapping to taller gears. I have a 4.10 MX-6 gearbox in my ZE and even that is geared far too short. The KL in the MX-3 hardly needs such sort gearing so it's good to see a good solution has been found. I believe I was at 3300-3500 cruising at 110kmph recently (almost 70 mph). It's just ridiculous if you were to cruise at a higher speed, the engine is making far too much power,

it's like you've permanently geared down to overtake.

I know, I loved it! Was on the K8 trans too, and she was just ready and wanting to go. Just crusing, you can feel it felt like you were just giving it milimeters of throttle, and that's part of where the fuel economy comes in because of these motors needing revs to make the torque, and you need torque to move the car.

Cruising beyond 120kmph (75mph) at almost 4K is absurd

That's typically normal for low torque cars, Japanese especially. My sister's H32 Prelude was, my Mx-3 was and my Rx-8 is like that too.

Before you embark on this mission to change your gearing, I would highly recommend to install a vacuum gauge in your car before hand. You can gauge the engines workload with the gauge and you can see how hard she's working, and you'll be able to compare after you've changed the gearing.

Before I embark on this mission I'll have to confirm with crazycanadian (after reading all the pages of his build at clubprotege) what exactly I need to swap over for the taller gearing. Just the 3.85 Final drive off an escort of some year might be enough?

[Nd4SpdSe]

A mission, a year and a half in the making

[RX8SE3P]

11000 posts; how many of which are useful I wonder?

[Nd4SpdSe]

Guaranteed more than 885