tranny problems?????

[ropinfool2]

Howdy all, Finally had a chance to load up the truck and put it to work. I hauled my 5th wheel, (11,500 gvwr, not weighing anywhere near that) a couple hundred miles round trip camping. Hit some pretty good hills and don't think the tranny is shifting right, but you tell me. Pulling a hill in OD, foot buried, speed holding at 65, ok, speed starting to drop, 60, tranny downshifts, ok that's what it's supposed to do, speed drops to 55 and tranny UPSHIFTS!!! Went from 2500 rpm to 1800 rpm. truck falls on face. My foot is buried. Pull my foot off and jam it back down and truck downshifts, ok, holding speed, after 45 seconds or so, upshifts again!!! WTF???? Reach the top of hill, ****** off now. Hit cruise and watch what it does, pulls the next two hills just fine but the 3rd hill doing the same thing, speed drops to 45 and it still won't downshift!!!! Was just getting ready to pull it into second manually when I see brakelights. Border Patrol checkpoint. This really has me stumped. I've never seen this before but have never pulled a load like this before. Is this what you guys are seeing????? Oh and I avg. around 9 mpg on the computer so it's closer to 7. I'll fill up tomorrow and avg it out. No SES light, haven't checked for codes using the key thing yet. Thanks in advance. John