Hey Chevyman. I have a 04 Venture (4t65e tranny) with 114,000 Km (approx 70,000miles) with hard shifts and code P1811.
There is a thread under the Buick forum with a lot of good info
http://www.automotiveforums.com/vbul...79#post6816779
Have you had any problems since installing your Transgo shift kit?