I seen you had a problem where you wanted to hold in 4th gear and not let it go to 5th.. I found a resolution to it... please visit

http://www.kennedydiesel.com/docs/Al...ut%20final.htm

This shows you how to hook up a switch that allows the transmission not to shift into 5th until you turn it off.. I have used this and it works great. It is involved. The transmission is equipped with the lockout from 5 the gear but GM never used it.. Allison has gave the information out.