For what it's worth, 2-3 lockup 700R4 good for 1 MPG
In my quest for even a little better MPG in my Jimmy I tried using 2-3 lockup on the 700R4 using the method shown on Crosley's website. Gained 1 MPG and with a flip of a switch can go back to 4th only lockup. May not seem like much but driving 80 miles a day it adds up. What I found interesting is that I never thought I spent much time going through the gears being that most of my driving is at highway speeds. Don't know what this is doing to the tranny, but it already has 225K miles on it and nothing lives forever...
BTW this is in a 91 S15 Jimmy with a 350 .030 over, Summit 204/214 cam, Quadrajet, headers, duels, 3.42 gears, 16.5 MPG before 17.5 MPG W/2-3 lock.