Story of a custom 5th gear for a '98 Ford Escort ZX2: +6% MPG

[livewire516]

Originally Posted by niky

This can easily be done with any BJ Mazda Protege with the 2.0 manual. The MX6/Probe/626 used the same gearbox, and both final drive and 5th gear are longer. Swapping 5th gear alone is painless and lowers cruising rpm from around 3200 at 100 km/h to around 2900-3000.

Even better, if you can order a fifth gear from Europe, the 5th gear from the diesel Familia should lower cruising rpms to under 2500 with the same final drive, and it would likely be much more durable than a custom-ground gear.

How could someone source a European 5th gear from a diesel? I'm trying to improve my Protege5's highway mileage.

[niky]

You'd have to figure out the part number, then order it from Mazda there.

The 626 gear swap is easier. You can get it either from the junkyard or online via a regular parts supplier in the US.

[mazdamx640]

I'm wondering if something similar can be done with a getrag f23 out of a cavalier. I'm going to be using one with a 3800 and the 4cyl transmission isn't suited for the low rpm cruising the v6 is capable of

[19bonestock88]

The F23 transmission was available in multiple final drive ratios. Cavalier used something like 3.84 or 3.94 but the Cobalt XFE used 3.63 final drive. All of the F23 transmissions are physically the same I think (other than front trans mount point)

[MeteorGray]

My 2015 Mazda3 with the 2.0L engine and six-speed automatic does pretty well. It has a final drive ratio of 3.59 and a final 0.60 overdrive, equating to a final drive ratio of 2.15. This allows me to cruise at 70MPH at 1950RPM on the 20565R16 Bridgestone Ecopias I am currently running, but my prefered speed for better fuel economy is 60MPH at 1670RPM.

With 155HP, I doubt this car would benefit from any higher gearing. It's got pretty long legs from the factory and seems to be quite well specced.