I have this happen about 2-3 miles after starting out. I always dismissed it as hitting a bump in the middle of the intersection and losing traction. Usually under heavy throttle.

I have just noticed that this is happening during a shift starting from a full stop.

The dash rattles from the slam, then the rear tires screech, and the shift finishes. The entire rear of the truck acts like it hit a bump.

Is this a normal harsh cold shift or is the transmission locking up during the shift?

2008 2500HD crew cab long bed 6.6 Diesel 64,000 miles. Stock. 5th wheel setup 50% towing miles. ECM flashed with the no start recall. Trans oil serviced, oil and ext filter, at 25K and 50K with internal filter changed at 50K.

cool, wish mine would shift half that hard. I hope its not serious.

I would take it to the dealer since it is still under warranty. I'm pretty sure the tranny will not like the hard shifts for much longer. On the good side when it lets go for good it will be easier to find the weak link.

^^^ Not funny!!!haha.