Subaru Impreza 6 Speed Swap

[wanderlost]

Hey guys! These forums appear to hold a huge wealth of knowledge. I have a 1993 Subaru impreza fwd with a 5 speed. I know subaru put 6 speeds in some of their more sporty go fast models. I am still researching to see if I could find a 6 speed out of one of those models that would fit in place of my 5 speed. My theory behind this would be to drop my highway cruising rpms with a 6th gear overdrive to return better highway mileage. Currently I am averaging 33mpg in mixed driving and 30 on the highway turning 3000 rpm at 65-70mph. My wheel nut has a couple screws loose so it is constantly getting tweaked for better mpgs. Any input/ knowledge would be greatly appreatiated!

[brucey]

The only 6 speeds I'm aware of are AWD and geared very short.

Even if you could convert an AWD 6 speed to FWD only you would likely not see much gain because of the gearing problem.

Example:

5th in a 5 Speed Impreza is 0.780
6th in a 6 Speed STI is 0.756

A real gain of 0.024.

You might have an easier time finding a taller final drive.

[Stubby79]

What he said. AFAIK, they went all AWD a decade or two back.

[iikhod]

Maybe higher diameter wheels? Unless you drive a lot of stop&go.

[cRiPpLe_rOoStEr]

Usually those "sporty" 6-speeds have a narrower gear-spread, thus resorting to a shorter differential in order to provide them with some agility at the acceleration. So it wouldn't be really so useful.

[wanderlost]

Good to know about the gearing. I did upgrade from 13inch wheels to 15 inch wheels with a much larger tire (they ended up weighing less than the stock 13s?) And gained almost 2 mpgs.