Kia Rio B6 --- Transmission Compatibility?

[RioBravo]

I'd like to lower the cruising RPM of a stock Rio by swapping in a longer 5th gear and final drive. I apologize that this isn't directly Festiva related, but the Rio has little enthusiast following on the internet. Since it's the successor of the Festiva/Aspire, I was hoping to tap into your community's knowledge.

Is the Rio transmission a derivative of the Mazda F-Series or G-Series transmission? The Festiva and Aspire used F-Series transmissions (right?) so I assume F-Series. The best donor candidate looks like the 1991-1996 Escort 1.9l transmission, but the bell housing and axle splines seem wrong. Will the guts of the 1.9l Escort transmission fit in the case of the Rio transmission? To avoid sourcing new axles, do you think I could swap the old spider gears into the new differential?

Is there a better direction to take? Is the Rio engine/transmission combination a unicorn with no swap potential? I appreciate any help you can offer.

[theastronaut]

I've seen Rio trans swapped into a Festiva, you should be able to swap a Festiva trans into a Rio since they're geared longer. I believe the Rio is an F series. Beware of dropping the ratio too low and not having enough torque to pull the car up hills or at higher speeds with more aero drag, especially running the A/C.

[RioBravo]

Thanks for your help. I found this thread from the past: https://www.tapatalk.com/groups/ford...ion-t1854.html

It looks like the Festiva is an E-Series transmission with a smaller clutch (<185mm) and bell-housing compared to the Rio (200mm). Are the bell-housings swappable? Does the Festiva use 28 spline axle shafts? Will the Festiva transmission handle 33% more torque from the B6 engine?

On another note, are the internals of each series transmission completely swappable? i.e. F-Series guts from transmission A to F-series case of transmission B?