Sergio,

on Futaba non computer TX's, it is usually just a small spring and a ratchet/leaf spring that you need to exchange from one stick to the other.

Take the Tx back cover off and on each stick you will see centring springs while on the throttle stick , you will see a small leaf spring which engages the throttle ratchet.

Swop over the leaf spring plus the ratchet with the elevator spring between the 2 sticks and thats that. You will see the screw holes for the ratchet on the other stick position.

Its tricky handling the small spring and engaging it on the hook - I use a very small screwdriver to catch end of spring and slip it over the plastic peg.

make sure you pick the right spring!!

On some Tx's it is only necessary to shift the ratchet and leaf spring and leave the centring spring where it is. If you can count 4 springs, then only swop ratchet etc.

If only 3 springs then you need to shift centring spring as well

hope this helps

John