When I apply the brakes and I am just about stopped it feels like a load shift foreward (no load in the box). Definitly in the transmission.
05 Duromax. Any ideas?

You need to grease the slip yoke spline. When dry as mine was, it will clunk just at the point where you come to a stop. There are many threads on this forum that talk about this condition, and also recommended greases to use. Just search "slip yoke spline clunk".