While driving to Calif. from Ariz., on I 10, dropping down into Indio on a mild grade, at 75mph, when I came to the steepest section the transmission down shifted, rpm’s rose and it felt like the engine was keeping the mph at the set speed, by providing more drag which it did. I have had many auto with transmissions and cruise control, been descending steeper grades, and never have had this happen. The vehicle is a 2014 Avalon. It would be a nice feature if it had been designed to do this auto braking, but I don’t think that it ia supposed to do this??? Would appreciated any thoughts/enlightenment.
Yes, it is operating as designed. My 1996 Dodge will downshift descending grades with the cruise control on. I usually switch the cruise off before this happens. I don’t mind gaining 3 MPH, rather than listening to the engine race. If the vehicles speed increases too much I manually downshift.
I’m not sure of the operating system your car uses, but it’s common for a car to do that. Sounds like a modern-day cruise control operating as designed.
Your Avalon may be equipped with Adaptive Cruise Control (ACC). It’s on option on high end vehicles and will slow your vehicle down when necessary to maintain the proper speed.
Modern automatics often have hill detection built in - when they see that you’re on a downhill, they’ll downshift to keep your speed constant. Some even work without cruise control engaged at all.
For what it’s worth, my wife’s BMW X5 can actually apply the brakes when going downhill if necessary.
It’s normal. I have a 2004 Toyota Sienna and, with cruise engaged, it will downshift while going down steep hills to help keep the speed of the vehicle in check. If it were Adaptive Cruise Control it would slow you down if you were approaching a vehicle in front of you.
Sorry to be a “kill joy”. But if you won’t read the owners manual I’m not going to do it for you.
^
What’s that old saying?
When all else fails, Read the Manual.
Or, alternatively, one could spend much more time and energy by going online to ask random strangers about what is contained in the manual that lurks–unopened–in the glove compartment.
I know Chrysler vehicles have done this for at least a decade. I’m not sure if other manufacturers’ vehicles are programmed to regulate speed in this way.
Do the “read the owner’s manual” comments add any value to this discussion?
Or do they help to make sure the OP never returns?
I couldn’t find a description of this feature in the owners manual or service manual.
This is the only mention of transmission behavior on hills that I could find;
Engine speed while driving
In the following conditions, the engine speed may become high while driving.
This is due to automatic up-shifting control or down-shifting implementation to
meet driving conditions. It does not indicate sudden acceleration.
●The vehicle is judged to be driving uphill or downhill
●When the accelerator pedal is released
Aw, come on guys, take it easy on the OP. Haven’t we established in another thread that owners manuals these days can run to 1000+ pages, 800 or so of which are safety warnings written in lawyerese.
Or maybe there is no paper manual, maybe its on a CD-ROM and when you insert the CD-ROM you get a message telling you to upgrade to the latest version of Adobe Acrobat, and your computer won’t accept the latest version of Adobe Acrobat unless you upgrade your operating system for $119.00. Or maybe you’ve got to wade through a half-dozen “special offers prepared especially for you” before you can get to the start of the owners manual. Just sayin’ 
@Nevada_545: The excerpt from the owner’s manual that you posted seems to describe that the transmission will downshift to regulate speed. However, they must have hired someone that aspires to a job in the insurance, legal, or medical industries to write the manual, as this passage is anything but clear and concise.
A friendlier way of putting it might be: “When descending a hill with the cruise control engaged, the transmission may downshift to brake the vehicle and maintain the selected speed. You may notice the engine RPMs increasing when this happens. This is normal.”
I don’t think that excerpt from the owners manual has anything to do with cruise control. It describes normal automatic transmission operation, albeit in very poor english.
I rented a chrysler 500 a while ago, and it had this feature (downshifting under cruise control) and I didn’t like it, but it worked.
I’ve ridden in a 2014 Sentra that downshifts when the driver applies the brakes when going downhill.
There is nothing in the cruise control section of the owners manual that describes transmission down shifting, the statement that I posted was found in a different section.
"There is nothing in the cruise control section of the owners manual that describes transmission down shifting, the statement that I posted was found in a different section."
Similarly, I have found information in Owner’s Manuals printed in sections other than where I would have expected that info to be placed.
Poor editing?
Illogical thought patterns on the part of the people who compiled the manual?
Who knows?
The bottom line is that it behooves car owners to read the entire manual–at least once–after purchasing a vehicle. Even if it takes a few days to slog through it, reading the manual is potentially very important in order to prevent problems. Afterwards, it is sometimes helpful to re-read specific sections in order to find the information relating to a particular problem.
Poor editing? Illogical thought patterns on the part of the people who compiled the manual? Who knows?
Pirsig had something interesting to say about that. His theory was that the manual writer goes down to the factory and asks the foreman to get him someone to explain how the system works. The foreman doesn’t want to lose any more work output than he has to, so he grabs the most useless guy on the floor and sends him to explain the thing, which is why manuals are so often terrible at telling you how the thing actually works.
My Kia with manual transmission does not do this.