Mazdaspeed Protege Transaxle/Transmission Mega Guide and Interchangeability Guide

Last updated 9/20/2018
These are the available transaxles that can be used as bolt-in replacements.

G15MR – 2003-2003.5 Mazdaspeed Protege w/ factory LSD option, best exact factory replacement.
G15MR – 2003-2003.5 2.0L Mazda Protege, Protege5 no LSD, closest to factory replacement
G15MR – 2001-2002 2.0L Mazda Protege, Protege5, MP3 no LSD older 5th gear synchro design
G25MR -1993-1997 4 cylinder 2.0L Ford Probe, 1993-1997 Mazda MX6, 1993-2002 Mazda 626 no LSD older design shift fork, oldest 5th gear synchro design, wrong gear ratios depending on year
G25MR -1993-1997 V6 2.5L Ford Probe, 1993-1997 Mazda MX6, 1993-2002 Mazda 626 no LSD older design shift fork, oldest 5th gear synchro design, wrong gear ratios not optimized for turbo 4 cylinder

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.
By using any of the older transmissions you are using an inferior and outdated design.

Output shaft out of the 03+ G15MR(bottom) vs the older G15MR/G25MR (top). This change affects the 5th gear synchro design as show below.

03+ G15MR > 01-02 G15MR > G25MR 5th/Reverse Synchro Assembly

G25MR > 01-02 G15MR > 03+ G15MR 5th/Reverse Synchro Assembly

03+ G15MR > 01-02 G15MR > G25MR 5th/Reverse Synchro Assembly

03+ G15MR > 01-02 G15MR > G25MR 1st/2nd shift forks

Version 1 (2 left)Vs Version 2/3 OEM Mazdaspeed LSD

Common Broken OEM Mazdaspeed LSD

Open differential from other non Mazdaspeed transmissions

Steel case reinforcement plate

Original Mazdaspeed G15MR organic lined synchros (bottom 3) that are no longer used due to ease of failure and incompatibility with certain oils

Current brass synchros with small oil channels to allow the oil to escape for faster and smoother shifting.

CrossoverAuto.com Dual cone synchro conversion for 1st/2nd gear left vs stock right

CrossoverAuto.com Dual cone synchro conversion and straight cut PAR gearset for 3rd/4th gear

Use API GL-4/GL-5 75W90 gear oil. 80W90 (use only above 10°C/50°F or it will shift roughly in colder climates.)
Only the MSP has the weak factory LSD option, notorious for breaking in half at the casting.
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.
Mfactory is the best alternative option. Don’t even bother using a Phantom Grip on converting open differentials. Quaife is good but the hardware fasteners to install it are hard to find.
The Quaife fits the MSP and regular Protege axles, thus any Protege M/T axle will interchange as well. MSP axles are strongest due to being 2mm thicker
GTX gears are not stronger replacements, they still have failed.
Stronger replacement gears are made by MFactory (500hp version) and PAR straight cut gears.
PAR is the only one that has a synchro upgrade option
The weak transmission problem still lies in the aluminum casing 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. The bearing cups also come loose and spin in the aluminum casing causing deflection and movement.
PAR still makes a bearing cup reinforcement. Ferdi made a steel case plate that requires machining which will help alleviate some of this problem. Hydra/Exile replicated this plate and we believe they are inferior to Ferdi’s version. We installed 3 of the replicated versions and found large variances in the machining plate tolerances where proper shimming was not attainable without major work. Use a micrometer to measure for yourself before machining your case for those plates.
The clutch housing side is still weak where and there are no manufactured solutions available to reinforce the bearing load on that side
PAR also can make a full gearset 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 and the gear.
Be weary of using unknown high pressure plate clutches, they will put undue stress and wear on the hydraulic assembly, clutch release fork, throwout bearing, and the crankshaft thrust washers.

Pressure Plate Ratings
OEM Mazda (made by Exedy/Daikin) stock non-turbo Protege pressure plate has a 1169 ft lb clamp load (aftermarket OEM replacements at the auto stores are for this model)
OEM Mazda (made by Exedy/Daikin) 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 Racing Stage 1/2 pressure plate has a 1545 ft lb clamp load

Exedy Stage 1 or 2 is going to be the closet to the factory MSP clutch pedal feel because they do not have as high as a clamping pressure as some other manufacturers. These make excellent replacements for a mildly upgraded vehicle that is street driven.

CrossoverAuto.com recently released a twin plate ceramic clutch for high horsepower builds 300-900hp that current single plate performance clutches cannot hold.

The MSP clutch master cylinder has a delay valve added to the port where the hydraulic line connects to slow the return of fluid back into the clutch master cylinder. This reduces sudden torque surge into the drive train to mitigate transmission damage. Removing the valve or switching to a N/A protege clutch cylinder will provide a different clutch pedal feel.

The MSP clutch pivot and clutch fork use heavier duty components to handle the stiffer clutches better.

The stock MSP flywheel is exactly the same weight as all the other 2.0L proteges
The JDM mazdaspeed flywheel is from the Japanese MP3 Mazdaspeed Familia is the only OEM lightened version.

Find an online gear speed calculator to determine the mechanical top speed in each gear.

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 – All 01-03
1st: 3.307
2nd: 1.842
3rd: 1.310
4th: .97
5th: .755
Rev: 3.166
Final: 4.105