Weird Acting Cruise Control

I recently took a 4.5 hour vacation trip down to the coast of South Carolina. I have a 2016 1794 CM 4X4 with 295/70 R18 Tires. I had the Tundra loaded down and also pulling a 18.5' center console boat and running about 70 MPH on the interstate.

I don't normally use cruise control when towing, but I thought I would see how it worked using the Tow/Haul mode and under a heavy load. All was good until going up a steep incline and dropping from 4th to 3rd gear. The truck speed dropped off significantly as the cruise control acted like it was limiting the motor to around 4,200 RPM. If I pressed the pedal, the RPM's/speed would increase and eventually shift back to 4th gear. This problem was slightly better when not using the Tow/Haul mode and probably due to the change in transmission shift points.

Has anyone else seen this problem? Is there an easy fix?...not a show-stopper, but seems maybe there might be some sort of software update I need for the cruise control.

Ok for the wise guys: Yes, I could slow down a bit!

Thanks in advance for any advice.

 

I dont think there is a problem. Cruise control is slower to react the you when driving. I do some towing and use it but when it gets hilly, the cruise control tends to make the truck shift a lot more, unlocking the converter. So, I use cruise on fairly flat terrain, if you are in hills, just control the throttle and gear yourself.

Also, suggest that you do not use drive, use s4 or s5 when towing anything over a few thousands pounds. It will keep the trans temps down and converter locked. The engine will spin up more, but you will in fact get better performance, MPG and less wear on the truck keeping it in the powerband.

 

Many Thanks for the good comments and advice. I won't use the cruise when towing, but thought it odd that the RPMs seem to be limited when it dropped down into 3rd gear.

 

Probably a motor protection feature. You don't want cruise control to have the ability to redline your engine. Not good.

 

Good point. That would explain it. Thanks.

 

Guess I can use this as an excuse with the wife to get that Supercharger I've always wanted...

 

I use CC when towing all the time, but we are mainly flat. When I do hit a steep incline or decent, I disengage until I'm flat again.

It's too wonky on hills. Shifts all over the place. Our Sienna was the same.