The new tow ratings in the 2018 Trailer Life Guide to Towing shows the Chevrolet Suburban with a 5.3L V-8 engine and a tow rating of 8300 lbs. This is not enough to tow my existing (and last) TT (7500...
Interestingly enough, I tossed the new Tow Ratings Guide as I'm not in the market. But............is the Suburban you mentioned a 3/4 ton? If not, that would answer all your questions. 13000 sounds like the new standard for a 3/4 ton and 8300 sound very 1/2 ton-ish