Ken, I had the same problem with my truck and the remedy was to adjust everything according to the book. The sad thing is I forgot what book I read it in! It was probably the shop manual. I will look for you if you want. I know I had to adjust up the cables first and then the release rod measurement was critical. It was only after all this that mine would hold.
Mothertrucker, I'll answer your question you asked on another tread, as to the Duramax, it seems to be alright and the only problem was that the bolts from the factory were not tightened on the torque converter. :p
