Hi Doug, I could not reply to your post for some reason. I have never heard of this happening. Are you coming to a rolling stop, then hitting throttle hard? If this is the case, you may be between gears when you hit the throttle and this would cause the bang. Are there any codes? Press both arrows at the same time and if OL comes up, press again. What you want is D1 and if anything besides - comes after D!, let me know and I may help. I would also pull the plug and check for metel in your differential. Please let me know of outcome of code check or call me at work 7-3:30 PST at Pacific Detroit Diesel Allison in Ridgefield, OR @ 360 887-7556. Thanks and have a great day!