Just installed a Tri-Ax for 3650 yesterday, loving it. The difference is amazing, I highly recommend this mod.
This is my second Tri-Ax install; I helped a buddy with his T45 a few months ago. There are several good web sites around describing the install; I just thought I'd share a few experiences and pointers from my two installs:
1. Getting the stock shifter off: The instructions say something like "a blow from a block of wood will help dislodge the old shifter." What they mean is take a two by four or equivalent, anywhere from 6 inches to two feet long, whatever you have, set one end against the metal 'tower' of the old shifter after you've removed everything else - then whack the other end of the two by four with a hammer a few times. Repeat on the other side. Use any other method and this step can be the most difficult and time consuming part of the install. On the T45 install, this step took us 2+ hours of pulling and prying.
Trust me, the two by four is your friend.
2. The only difference between the TR3650 install and the T45 install is the little plastic cup that fits on the arm between the shift lever and the transmission. On the T45 the cup is loose and just sets in place, on the TR3650, the cup snaps into place. You must pry the cup loose with a screw driver to get it off the old shifter - use caution, I was prying away and launched the cup across the yard. Getting it back on the new shifter is a pain as well - just push really
That's it, took about an hour (way less than the T45 due to afformentioned 2x4 trick), mainly taking out trim and bolts. Get ready for some awsome shifts.