I towed 5,500# on a 29' trailer with a 2011 Avy LTZ. Not a good experience. Power wasn't a problem (I had a 3.73 put in and had a tuner) but the soft air ride suspension just didn't work well. There are better tow rigs out there but moving to a shorter, lighter trailer should help you a lot. Your older Avy has the four speed and hopefully you have the 4.10 rear. But with only 4000#, you should be fine. From my experience, maxing out on payload with the Avy isn't a good idea. Check your door sticker for you payload. Mine was 1,060#.