Replacing Tranny / upgrade
 

I am currently driving a 99 Civic with a 4-speed automatic transmission that is dying a slow death after a fault free 325,000 mile life. The plan, when it finally does die, is to replace the original transmission with a junkyard tranny. I don't believe that I am forced to replace with the exact same part number. The Civic offered several transmission options, so I should be able to refit with a 'high mpg' gearbox. Has anyone upgraded (mileage mod) a tranny in this fashion?

Results/ problems?

Ideas and suggestions welcome!

Thanks guys. The level of response has been stunning.

Lol :)

I put a stick in my saturn after the auto died, took a long weekend and a $300 parts car and a $30 "manual" computer for my year to make the obd happy (parts car was pre-obd but everything else bolted up). Entirely doable, I wouldn't do it for anything less than a stick shift though.