currybob

I have a 2017 RX and have noticed, after setting the cruse at a set speed and then if going down a hill it will downshift transmission for even 1 mph over the speed setting. Anyone else's doing the same?

Bob

Supranut

I have a 2016 RX350 F-Sport and it does the same thing. It also does it when you try and reduce the cruise control speed by using the cruise control stick.

dchar

I think the system is trying to use engine braking to slow the car down before applying the actual brakes so that the brake lights don't come on every time you slow down a little bit.

guanche2k9

Hi everyone, newbie here. I recently picked up a 2017 Lexus RX 350, and been having an issue with the cruise control. Took it to the dealer, and they said it was a normal behaviour due to the 8 speed transmission (I don't think so).

Here's a description of my problem with my 2017 Lexus RX 350:

When I set the cruise control to a certain speed (doesn't matter the speed it's going - but I usually set it between 55 and 65 MPH), and then try to decrease the SET speed below the previously SET speed (say from 60 MPH to 57 MPH), the RPM's will jump up to about 4,000 RPM, stay for about 3-4 seconds, then decrease to 3,000 RPM, stay for 3 to 4 seconds, then decrease to 2,000 RPM, stay 1-2 seconds and finally settle into cruising RPM's at around 1,800 RPM.

Is it normal for the engine RPM's to jump up when I decrease the SET speed on cruise?

Your feedback would be greatly appreciated. Thanks!

stevez2

Have not noticed any cruise control engine rpm issue in my 2017 Rx350- but then again I am probably not monitoring the tachometer while cruising down the road. Assume that the car is responding to your request to decrease speed by downshifting rather than applying brakes - which is probably normal.

syntxerr

Those 8-speed transmissions tend to jump around the gears quite a bit. When I'd go down a hill in my IS350 at 70 or so, the cruise control would shift from 7th to 8th to 7th to 8th and so on, using engine braking instead of the actual brakes. However, it would get up to maybe 2000-2500 or so... 4000 seems a little high.

Could you take a video for us?

Oldfart

Instead of using breaks computer is using engine and shifting through gears.

LordBowral

Sounds normal to me ....

ggebhardt

I have noticed this behavior on my now sold RX350 and stopped decreasing the speed with the cruise control. I would just reset it to the new speed.

dfc350

It's downshifting to slow the car to the speed you requested. Sounds okay to me.

dougef

Have noticed this behavior using cruise control when there is a reasonably steep downhill on the highway - uses the engine to slow the vehicle on the downhill. Never noticed this on other vehicles, but seems to be the way it was designed.

guanche2k9

I'll see if I can record a video next time. The car is still at the dealer for another issue that they can't seem to resolve (a bubbling noise coming from under the car when going at slow speed - 5 MPH - 10 MPH).

It's the first time I see and experience a vehicle using engine compression (downshifting) to reduce the speed on cruise control. I do agree that jumping up to 4,000 RPM is a little high. Nonetheless, as soon as I get the vehicle back (hopefully this week), I will record a video and post.

mikemu30

That will even happen with some 6 speeds.

mcomer

Try changing the Drive Mode to Sport and see what the transmission does during your deceleration command.
While you are at it, try again with the DM in ECO. I think everyone contributing is correct, it is the transmission
trying instead of the brakes to slow you down, Drive Mode ought to change the Transmission behavior.
Let us know...

guxu

I saw the same today. And I think it is normal.