I have a '13 GS350; when the car is in cruise (generally between 80-90mph) if I am descending down a hill, the car shifts back and forth repeatedly between gears. Imagine driving on a flat surface and giving it a little gas and letting off, then giving it some gas again and then backing off. Super irritating. Any ideas?

 

What transmission mode is the car in? Normal, sport, etc?

 

Mine does the same thing I think they were engineered like that, why??? idk! but its to keep the car at the selected cruise speed.

 

Mine does the same thing, and I've heard from others theirs do too. Very strange.

 

Of course it does! The torque converter transmission is using engine braking and gas to keep you at the set MPH. Because the grade (slope) is constantly changing it has to go back and forth between engine braking and gas to keep you at the desired speed. My only suggestion (if this bothers you) would be not to use cruise control unless driving on flat surfaces.

 

It's always in normal. I haven't had it long. Only used the paddles once or twice.

 

This behavior is NOT normal or typical as you suggest. I've owned many cars, all with cruise control, including many Lexus vehicles and I have never owned a car that behaves this way with cruise set and going down a grade. The shifting is rhythmic up and down at an exact interval. You can watch the RPM go up and down to the same two spots every 1.5-2 seconds or so like a stutter. Very bizarre.

It's obviously normal for this car, but it's a design flaw IMHO

 

Mine does that when going downhill as well. I just turn off cruise control.

 

Not my first Lexus or car....I have never known any car to do this including previous GS. The wife's RX doesn't do it. Sounds like it is a querk that a unique to the 6speed ('13) GS. Thanks for the response folks!!

 

Totally agree!!

 

Anybody who wouldn't agree is either not being real or hasn't experienced it. It is very obviously not right...it's not the end of the world but to say "all cars with torque converters do that in cruise" is just wrong. Although, if I drove in conditions that made this happen all the time I might just think it was the end of the world.

I haven't bothered to say anything to the dealer because I know lots of other people here have the same issue.

 

I know what you mean the shifts are very fast back and forth as though its just constantly shifting as opposed to holding any gear. I have experienced it and it doesn't feel wrong to me at all. I doubt this was overlooked by engineers but rather behaves this way (differently than previous Lexus transmissions) for a reason. All torque converter transmissions set in cruise going downhill DO shift back and forth to maintain the set speed. Obviously every car will behave differently when doing it but they all do it. "It is very obviously not right" How So? The fact that everyone is experiencing this tells me otherwise.

 

So that's not entirely true. I completely agree that this is normal behavior for this car and many others ( a number of GM cars have this feature as well ), but it's certainly not every car.

My Titan doesn't downshift on a grade when on cruise control, it just runs away from the set speed... that's much more annoying in my mind because if you hit the brakes to control your speed, you've now canceled cruise control.

It's certainly a feature not a flaw. However, there are a number of non-lux cars which don't do it so I can imagine someone's surprise.

That's just a bit silly though =)

 

I completely agree. Sorry for not being more clear but i meant torque converter transmissions with the ability to maintain set cruising speed traveling downhill.

 

LOL, I don't know what to tell you. A car should not buck back and forth every 2 seconds when driving down the road at a set speed. It feels very unnatural and unintentional. No car I have ever owned or have ever driven behaves that way. Anybody I have ever had in the car when it does that has always commented on it in surprise...so I suppose none of the cars they've ever ridden in or driven behave this way either. Every car I've owned including my 4 previous Lexus sedans can maintain a set speed when going down a grade by downshifting appropriately without bucking back and forth like a ride on bull. Obviously since this comes up lots of people feel its strange as well.

If they designed the transmission to behave this way, they need to go back to the drawing board