transmission issues

I have a 2014 GMC sierra 1500 C-cab short box 4x4 with the 5.3l and 3.42 diff gears. I have a 24 ft holiday trailer loaded about 5500 lbs and even on flat highway it is not surpassing 4th gear. I pulled my sisters trailer when their truck broke down and loaded it is 7700 lbs which is well within...

My transmission in my 06 sierra 1500 will go from 1st to 3rd but will not go into 2nd or higher. I tried using the manual shift to go into 2nd but it refuses. There are no engine lights or codes that show up. I took the trucking fishing and there was a large build up of ice around the...