Allison "hunting"

Good morning Mr. Phelps.
(Remember that from Mission Impossible T.V.)
You are providing a valuable and needed service THANKS!!!
I have a 2002 Chev 3/4 with Duramax and allison. At light throttle around cruising speed,the transmission seems to be shifting in and out of gear so fast it is allmost like a chatter (it feels like the engine is missing) so much so that to talk it sounds like we are warbling or talking under water. I took it to the local dealer who checked the "codes" and test drove it and said it was performing as normal. I noticed on one of the web sites that for 2003 they provided a lockout to prevent "hunting". I also noticed that you would only recommend one dealer in the Portland area who was competent with Allison.(my paraphrase). Can you recommend a solution and the dealer to take it to?