When I'm towing my 4000lb camper the truck RPMs at 2800 and only going100m/ph. When i'm using the manual shift mode it's shifting into 6th or if it is...the RPM doesn't change. (when i'm using manual with out towing it shifts into 6th fine and 1500 RPM at 100m/ph). Using the tow button with to without doesn't make a difference. I tried just leaving it in manual mode it didn't change the RPMs. Is this normal for a Silverado F150 LTZ 4X4 ?
My car has 111000 miles.
My car has an automatic transmission.
When a truck is towing a trailer or a fifth wheel, the engine will need to be producing maximum torque. The highest gear in most transmissions is the overdrive gear. The lowest gear typically produces the most torque from the engine and produces less and less as the shifts move up.
The overdrive gear means that the wheels RPM is actually higher than the RPM of the engine. This type of gear is not preferred when towing as it can do damage to the transmission. Due to this fact, Chevrolet has likely disabled the overdrive gear when towing a trailer.
If you suspect an issue, have the shifting issue diagnosed firsthand by certified technician, like one from YourMechanic.