2019, 2500 4x4,towing a 25' travel trailer, The exhaust brake does not work in first gear no matter what the rpm's are. Does it work on anyone else's? Also this transmission seems to hunt 4-5-6 all the time in the hills towing. A lot of times it only holds 4 or 5 for only a split second, Can the dealer help that sort of thing? I frequently tow my trailer down a steep grade that is 5 miles long with a comfortable speed of 10-20 m.p.h. Just wondering.