Last night I believe I finished my long transmission saga. I am theorizing that the Transgo shift kit I installed in my original transmission is what lead to its early demise. My rebuilds that had this kit installed all slipped in 4th. I even changed to a different valve body and then drilled the fresh separator plate the other day. The problem returned. I finally bought a Transgo separator plate from a transmission shop which has pre-set holes drilled and installed it with all the valve changes from the shift kit. My problem is gone and now the transmission finally shifts crisp and strong. My guess is that my instructions have incompatible hole sizes for whatever GM Goodwrench rebuilds have for separator plates. This is the type of the two separator plates I used initially. This also leads me to a question. Has anybody else installed the Transgo shift kit on a Goodwrench rebuilt transmission ? Any comments or suggestions on what may have been happening?