GM overstates 2014 tow ratings by almost 25%

The towing guide and order guide had correct information.

Your telling us that you validated towing in the Owners Manual before purchasing, and not the towing guide used online and in the dealer?

I suspect that GM informed you of this change, and now you want to make an issue since you did not truly investigate prior to purchase. Also, the GCWR was 14000. I suspect that you exceeded this if the trailer weighed 7600. So bought only on tow rating, and not GCWR.

Another tangential issue that has been mentioned several times is that no matter what axle ratio, the GVWR and the payload do not change. An 8000 pound trailer will have a tongue weight of 1040 at 13 percent and a hitch weight of at least 75-100 pounds. That represents a substantial amount of the truck's payload and leaves little for people, dogs, bikes, kayaks, etc. And it does not appear that GM made any mistake in the payload or GVWR caluclations that you (hopefully) considered prior to purchase. Like others have said, a half ton is still a half ton no matter what you do to it.

If this issue really keeps you from enjoying the trailer, the solution is to get a three quarter ton truck or a smaller trailer. First, I would take the truck and trailer loaded for camping to the scales and determine how far over or under you are regarding GCWR and payload. You may have been in excess of those parameters all along and not even knowing it. And apparently you insurance company did not know either or you might have received 'the' letter.