My trip down to Charlotte, NC last week was the longest trip I've taken in my 2018 F150 with Adaptive Cruise Control (ACC) My normal driving is City driving where I never engage cruise control and even if I make it to an Interstate, I rarely turn on the Cruise Control. I guess it's been a while since I used ACC and forgot how it actually worked, because I had several occasions where I had a similar experience to yours.
With Cruise Control enabled and set to your cruise speed, your truck will maintain that speed if there's no traffic in your lane. If there is someone in front of you in your lane, it will slow you down and pace the vehicle in front of you, leaving adequate stopping distance. If there is a vehicle behind you and no one in front of you, it will speed up to provide adequate spacing in case you need to brake. If you have a vehicle both in front of you and behind you, it will try to split the space in between. This is how things work when ACC is engaged and you don't touch the gas pedal.
What I forgot (multiple times) and I kept doing is that if you step on the gas, you override ACC and your truck will disregard any of the pacing, but ACC stays engaged until you a.) Step on the brake pedal or b.) Shut off Cruise Control.
The problem I had was I would step of the gas to override ACC in certain situations and then when I would take my foot off the gas, the auto-pacing of ACC would kick back in, so if you were too close to the vehicle in front of you, it would do what you describe where it would downshift very quickly to slow down. I don't know of the brakes were ever applied automatically, but I could see how this could cause an accident if someone is tali-gating you.
I stopped using Cruise Control after this happened a couple times to me to stop the severe downshifting (probably not good on the transmission) and to prevent someone from rear-ending me.
With Cruise Control enabled and set to your cruise speed, your truck will maintain that speed if there's no traffic in your lane. If there is someone in front of you in your lane, it will slow you down and pace the vehicle in front of you, leaving adequate stopping distance. If there is a vehicle behind you and no one in front of you, it will speed up to provide adequate spacing in case you need to brake. If you have a vehicle both in front of you and behind you, it will try to split the space in between. This is how things work when ACC is engaged and you don't touch the gas pedal.
What I forgot (multiple times) and I kept doing is that if you step on the gas, you override ACC and your truck will disregard any of the pacing, but ACC stays engaged until you a.) Step on the brake pedal or b.) Shut off Cruise Control.
The problem I had was I would step of the gas to override ACC in certain situations and then when I would take my foot off the gas, the auto-pacing of ACC would kick back in, so if you were too close to the vehicle in front of you, it would do what you describe where it would downshift very quickly to slow down. I don't know of the brakes were ever applied automatically, but I could see how this could cause an accident if someone is tali-gating you.
I stopped using Cruise Control after this happened a couple times to me to stop the severe downshifting (probably not good on the transmission) and to prevent someone from rear-ending me.
