lugging

Can’t tell if my truck has trans tune or not. It does have some random EFI sotf tunes. Doesn’t go into 6th until about 67mph. Converter locks up real hard in 4th. Unlocks noticeably going to 5th, then locks hard again (can really feel the torque when it locks though lol) Also seems to lug in...

So I was towing a 28ft travel trailer roughly 6,500 pounds on the interstate going about 70mph. When I would start to climb a hill I felt like I was lugging the motor with my foot to the floor struggling to maintain my speed. My rpms we’re jumping up to 2500-3000. The truck is an 07.5 6.7L 4x4...