Since the late 80’s, the G25/G5M transmission has been fitted to a number of vehicles including the 323/Familia, 626/MX6, and others. The G25/G5M series are a 5MT with variants including a number of gear ratio selections and varying final drive ratios. Throughout the model’s lifespan, single cone synchronizers were used early on with the gradual fitment of double cone synchronizers fitted to the later vehicles. This is the transmission of choice when the BPT engines or turbochargers are fitted to the BP engines in the Mazda 323/Familia/Protege or Ford Escort/Laser vehicles.
Although much stronger than the smaller F-Series transmissions, the G-Series torque capacity is still not sufficient to handle the extra load and shock provided by the fitment of more powerful engines and aggressive clutches with the most common failures being 3rd/4th gears, transmission case and broken differentials. The most notable weaknesses in the G-Series transmisssions is the general strength of the 2nd~3rd gear, differential planetary gears and pin. With more powerful vehicles, the case structure becomes a problem with the thrust load provided by the helical gears sometimes causing case failure including cracks in the housing and sometimes destructive failure of both housing and gearset.
For the extreme racer, we have available as a regular model the 1st~4th dog engagement straight cut gearset. Features include needle roller bearings on all gears and billet shift fork (3rd/4th) to provide the most precise and positive gear engagement at all times.
– Tooth profiles that reduce noise, wear and load forces on the standard OEM transmission housing
– Multiple piece input shaft for flexible ratio choice and changes
– Needle roller bearings provided with all gears for minimal friction, noise and maximum load capacity and reliability
– Retension of OEM 5th gear assembly provides OEM NVH levels during transport stages and freeway driving
– Straight cut gears for maximum power transmission and minimal thrust loads exerted on the OEM transmission case
– Billet Shift Fork provided for 3rd/4th gear
– Billet crown wheel and pinion shaft (Optional – $1,840 AUD (plus GST))
– Billet reinforcement cups (Optional – $650 AUD (plus GST))
– No extra cost custom ratios
– 1st: 2.55, 2.80, 3.11
– 2nd: 1.57, 1.83, 1.85, 1.90, 2.0
– 3rd: 1.24, 1.31, 1.60
– 4th: 0.90, 0.96, 1.29
– 5th: 0.78, 0.95, 1.05, 1.16 Optional custom ratios available
– Final Drive: Optional 3.93, 4.00, 4.08, 4.13, 4.43
– All Mazda vehicles that use the G25M and G25MR transmissions including Protege, 323, Mazda 3, MX-3, 626, Mazda 6, MX-6 and others
– Factory Service Data Specifications, especially preload specifications, must be used when installing gearsets