I had a similar problem with my Dyna, actually broke down on me twice. I got it to Harley the 2nd time and turned out to be the ECM, which was all covered under warranty. Any Check Engine light coming? I had that as well.
I doubt it's the transmission, it's probably either fuel or ignition. Did you recently get fuel before this problem started?
Unplug the PCIII and try it again...if the problem goes away it's in the PCIII if not it very well could be the ECM.
I had a scooter did this when the mixture wasn't quite right. Yeah a 50cc scooter with a mikuni carb. It's called "bogging". I would say it's probably a little rich. Especially at lower rpm's. Get your PCM checked. Worth replacing your fuel filter as well.
It turned out to be a bad PCIII. The dealer put it on the dyno and let it run until it started bucking and lurching after 40 miles. They swapped out the PCIII for a new one, and let it run for 100 miles and no more problem. I just took it out for 2 hours and it ran perfectly and there was no more popping on decel which was happening a lot lately. It even starts quicker. When I called Dynojet the other day and asked if they were getting calls about this problem, they said no. If you've been heaing about bad PCIII's, they'er either lying or in a state of denial.
They have an issue with compatability.They also refuse to admit there's a problem when the building is on fire.