4g15 gearbox extended 5th gear

CheetahSpeed (Jake)

CheetahSpeed (Jake)

Member
I current have a 4g93 manual, I’ll be upgrading to a hopefully cammed (depends how long my current engine lives) 4g94 in the future. I want to get the 4g15 box for the shorter gear ratios down low. But I don’t want to be revving the guts out of it on the freeway…

If anyone knows what gears from other gearboxes will fit in a 4g15 box. That’d be really helpful
 
Aren’t the top gears very similar between 4g15 and 93/94?

IIRC 1st gear is the only real difference. the 4g94 in my ch sits around 3k ish on the highway, but it really does need to. Not so much power and torque below that point at freeway speeds
 
SDate42 said:
Aren’t the top gears very similar between 4g15 and 93/94?

IIRC 1st gear is the only real difference. the 4g94 in my ch sits around 3k ish on the highway, but it really does need to. Not so much power and torque below that point at freeway speeds
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I want it to be even longer than the 4g93. I believe the g93 boxes are an 0.78 5th gear? I would rather like a 0.71 or into the 0.6s…

I drive my car (with the 4g93 currently) at 80 and even 60 in 5th gear and it’s fine. At 110/120 and 2.8-3k rpm it’s got plenty. It could easily be sitting at 2.2k or even lower and be perfectly fine

I was more just asking what gearbox parts fit what. Like fto gear parts, magma gear parts, etc. What internals will fit inside it the lancer boxes. So I can find the one with the lowest 5th gear ratio and use that gear instead
 
There was a 0.720 from memory in the 1.6 MIVEC model gearbox.
Obviously finding one would not be possible or economical, but perhaps you can buy the individual gears from amayama?

In any case though, the cost/effort will not be worthwhile to just get a couple of hundred rpm lower at highway speeds
 
Mitsubishi’s service manual on the F5M42 gearbox shows that the “highest” available factory gear for 5th is a 0.733. You will find this in any gearbox labeled
F5M42-2-R6N8 (EA6A chassis)
F5M42-2-F6NA (EA6A and EA6W Chassis)
F5M42-2-F6N5 (EA6A and EA6W chassis)

Provided your box is actually a 0.767 and not 0.820 or 0.804, this is the only listed Mitsubishi gear in your desired change for the F5M42 box.

Being as these are not cars sold here, you’d probably need to buy the gear by itself.

You can also check the F5M41 manual but I have no idea if the internals are interchangeable. I’m sure there are even more mitsubishi gearbox manuals you could look through, and take a guess at too.

Let us know how you go, be good to see it done!
 
I just popped the numbers through a calculator - with the change from 0.767 to 0.733 you can lower your rpm at 110kph by a mighty 112ish.

So you’ll go from approx 2800rpm down to 2700rpm.

Better off trying some larger rolling diameter tyres…

I genuinely do not think it’s a great idea to lug the motor at 2000-2300rpm where it has SIGNIFICANTLY less torque and power than at 2800rpm. But that’s just a personal opinion.
 
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