Transaxle/Transmission Interchangeability Guide

I will edit and update this post as I find out or recall more information, please do not quote this post so I can keep the thread clean with correct and up to date information.

These are the available transaxles that can be used as bolt-in replacements.
G25MR -1993-1997 Ford Probe, 1993-1997 Mazda MX6, 1993-2002 Mazda 626
G15MR - 2001-2003 Mazda Protege, Protege 5, MP3, MSP
The 2003 G15MR will have the most recent shift fork and selector hub revisions compared to previous versions, so this is the best one out of them.
Bonus
G35MR - out of the Mazda 3 is in the same family of G-type transaxles, gears and guts out of this gear box may or may not fit. I have yet to test or verify this theory. Someone who has access to one should check it out.

• Use API GL-4/GL-5 75W90 gear oil. 80W90 (use only above 10C/50F) or it will be too thick and will shift roughly in colder climates.
• Only the MSP has the weak LSD option.
• MSP trans has a stronger clutch throwout bearing release fork and larger fork pivot ball
• MSP trans has a different slave cylinder with a 1 way valve
• Some transaxles will have the speedometer gear which are not needed on the MSP, you can leave them in if you wish. The MSP uses the ABS sensors to determine speed.
• Quaife LSD is the best alternative option. Don't even bother using a Phantom Grip on converting open differentials.
  MFactory now has one available.
• The Quaife fits the MSP and regular Protege axles, thus any Protege M/T axle will interchange as well.
• GTX gears have been fitted to work, but still have failed. The real strong gears are PAR gears, however the problem still lies in the weak transfer case in which high rpm and high power loads cause the case to flex and the clearances for the main and counter gears to shift and grenade the gears. PAR makes bearing cup reinforcements which will help alleviate some of this problem, but not many except for some dedicated drag cars have tested this solution.
• PAR also has a full gearset available for those with unlimited budgets.
• Driveshaft shop used to make upgraded axles, but have discontinued their product application, they may or may not still make custom setups.
• If you have grinding issues shifting into gear, you will have to replace the gear selector hub and synchros together.
• Be weary of using high pressure clutches, they will put undue stress and wear on the hydraulic assembly, clutch release fork, throwout bearing, and the crankshaft thrust washers. The reason I recommend Exedy Stage 1 or 2 is because they do not have as high as a clamping pressure as some other manufacturers. The pressure on the Exedy's are slightly higher than the factory MSP which is already stiffer than a regular NA Protege.

Pressure Plate Ratings
OEM Mazda (made by Exedy) stock non-turbo Protege pressure plate has a 1169 ft lb clamp load (your aftermarket OEM replacements are for this model)
OEM Mazda (made by Exedy) stock turbo MSP pressure plate has a 1350 ft lb clamp load (there are no aftermarket OEM replacements for this clutch, you have to buy this at a dealer specifically for a MSP)
Aftermarket Exedy OEM non-turbo Protege replacement part# KMZ08 does not work on a MSP. You will be putting a non turbo protege clutch on your car if you use this! It will slip guaranteed!
Exedy Stage 1/2 pressure plate has a 1545 ft lb clamp load
Aftermarket performance upgrades
All other aftermarket performance clutches are rated against the non-turbo protege clutch.


Gear Speed Calculator
http://www.kabamus.com/garage/gears.html

Gear Ratios
626 I4
1st: 3.307
2nd: 1.833
3rd: 1.233
4th: .914
5th: .755
Rev: 3.166
Final: 4.105

626 V6
1st: 3.307
2nd: 1.833
3rd: 1.310
4th: 1.030
5th: .837
Rev: 3.166
Final: 4.105

Protege 2.0L
1st: 3.307
2nd: 1.842
3rd: 1.310
4th: .97
5th: .755
Rev: 3.166
Final: 4.105

I have a question about the clutch. With my mods, would an Exedy Stage 2 work? I had planned on picking up a Spec 3+ but would be interested in finding out from you about the Stage 2. I just want something that isn't going to produce harsh engagements, chatter, all that fun stuff. I have an Exedy Stage 1 right now, and it will slip at higher boost.

The Exedy stage 2 retains a spring hub but increases the torque capacity through a 3 puck using a cerametallic friction material.
It's going to have the similar pedal feel to the stage 1, but with slightly more chatter sharp engagement. Exedy revised the torque ratings after there were complaints about clutch slippage. The revised ratings are underrated now obviously.

The stage 1 is rated at 202 wheel torque. I would say around 230-260.
The stage 2 is rated at 229 wheel torque. I would say around 270-300.

You will have to go to a stiffer pressure plate with more clamping force around 2000 ft lbs or more. The Exedy clutches use 1545 ft lbs which keeps pedal effort close to stock.

ACT Xtreme, SPEC, Clutchmasters higher stage clutches are the only options until a multiplate clutch is made or you get a custom one made. Keep in mind they base the clamp ratings to the non turbo protege Clutches.

G35M-R internals should interchange fine with the G15M-R, but the differential cannot be used (regardless of the fact that it is an open diff)... the spline counts are different on the G35M-R diff, which means your stock protege axles won't fit in it

the MSP's clutch master cylinder is the same as the other proteges, except for an additional delay valve added to the port (where the line hooks up) to slow the return of fluid back into the clutch master cylinder... this is meant to reduced sudden torque surge into the drivetrain (to preven transmission damage)... this will explain why it is sometimes hard to dump the clutch on the MSP or hard to drive smoothly for the more experienced drivers... removing this delay valve will allow for more direct clutch feel at the added risk of drivetrain damage for novice drivers

the MSP's clutch pivot and clutch fork use heavier duty components to handle abuse better, they are parts binned from the MX-6 V6

the stock MSP flywheel is exactly the same as all the other 2.0l proteges, it is NOT lighter... the much talked about "mazdaspeed flywheel" is a stock JDM one for the Japanese MP3 (Mazdaspeed Familia), which is lighter

the transmission internals were changed for the 2002.5 MY, the 3rd gear synchro hub was redesigned and the synchro baulk rings were changed from a full bronze to a bronze/organic hybrid to address rough shifting concerns... the 1-2 shift fork was also changed, but no information about its strength is available, therefore it it politically incorrect to say it has upgraded shift forks... the 3-4 shift fork remains the same

nice thanks for this very informative guide..

subbin, Good info

Part Numbers

Does anyone have the part numbers for the Mazdaspeed Protege clutch slave cylinder and clutch master cylinder? I remember they are slightly different than a normal Protege, but haven't been able to find the part numbers.

So I can interchange my gears with a mazda 626 v6 cause 4th and 5th look better in thoughs ratios.

Yes, many people have changed 5th gear. You don't have to disassemble the whole tranny to change fifth, but you would to swap out fourth. I think the RPM difference for the fifth gear swap was about 200 iirc. Also, a few people have swapped in GTX gears (3rd in particular) and claim that the GTX parts are a bit stronger.