Downhill Downshifting

[reesesyum]

Hi everyone. I haven't found an answer to the following question:

When driving downhill (2008 yaris hatchback automatic), I sometimes depress the brake slightly to reduce speed. When I do this, the engine suddenly downshifts and the RPMs skyrocket. This can't be good for the engine. In addition, it's not the best for performance - going downhill I'd rather it up-shift suddenly, not shift into a lower gear.

I haven't found a solution to this other than to depress the brakes fully - but that's not the best option when I want to reduce speed only slightly when going downhill. I haven't experienced this in any other car I've driven.

Do others have experience with this? what's going on? any solutions?

[Loren]

Your automatic transmission is never going to downshift in such a way as to hurt the engine. Ever. Even if you tried to force it to, it wouldn't.

You might not like the sounds that the engine is making, but it's not hurting anything. Just turn up the radio and drive the car, already!

[Altitude]

Manual trans FTW!

[Maxh91]

Originally Posted by Loren

Your automatic transmission is never going to downshift in such a way as to hurt the engine. Ever. Even if you tried to force it to, it wouldn't.

You might not like the sounds that the engine is making, but it's not hurting anything. Just turn up the radio and drive the car, already!

+1 !

It's Engine braking. Your brakes is happy when Engine braking slowdown the car speed in a downhill.

No Engine braking + Downhill + Use brake = Death brakes (Overheat)

[mimelio]

That is a feature with the car

[Loren]

It's really more of a performance and economy feature. Downshifting keeps the revs up, and if the revs are up while you're foot is not on the accelerator, the ECU goes into DFCO (deceleration fuel cut off) mode and uses NO fuel. And, typically after one slows down, one then wants to speed up again, so downshifting while you're braking is a good thing, it means the transmission is ready to accelerate when you are.

Best solution: Just coast down the hill with your foot off of the brake.

[BLH]

Mine does the same thing. I have found how long after the hill is gone it upshifts again. Is very touchy to the exact position of the gas peddle.

[YarisSedan]

I always thought u were supose to purposely downshift the car to like second gear while going downhill. Instead of using your brakes. And just use the engine and transmission to slow the car down. If you are in a higher gear and constantly braking you are going to severely warp your rotors and cause brake fade. Cause your brake fluid to boil in the master cylinder and in rare cases crack your rotors.

Just shift down to a lower gear and use brakes as minimal as possible.

[gwasabi]

If you have a early 07, If you down shift too early in a manual trans while going downhills, your engine will stall lol

And honestly, Why would you downshift downhills? that's more pressure on the trans.

Downshifting lengthens the brake life but I would rather pay for new pair of breaks instead of repairing trans

[Hosh's One]

Originally Posted by Loren

You might not like the sounds that the engine is making, but it's not hurting anything. Just turn up the radio and drive the car, already!

Or throw it in neutral to get rid of the sound..haha..j/k

Originally Posted by YarisSedan

I always thought u were supose to purposely downshift the car to like second gear while going downhill....

Just shift down to a lower gear and use brakes as minimal as possible.

I always used to downshift when slowing down on flats too...one reason is to slow down faster and the other to "save the brakes"...BUT, I tend to agree with gwasabi

Originally Posted by gwasabi

And honestly, Why would you downshift downhills? that's more pressure on the trans.

Downshifting lengthens the brake life but I would rather pay for new pair of breaks instead of repairing trans

But still...would downshifting in general (excluding downhill) be almost as bad??..and what kinda RPM's is your car hitting when you experience the automatic downshift?

[Maxh91]

Originally Posted by gwasabi

And honestly, Why would you downshift downhills? that's more pressure on the trans.

Downshifting lengthens the brake life but I would rather pay for new pair of breaks instead of repairing trans

If the Yaris autodownshift in a downhill by itself...Why is bad to the engine and tranny?
The car was made for that. And you save gas!(DFCO)

About the wear on the brakes: Yes! brakes is better to change than a tranny but if the brakes overheat....

[gwasabi]

If you downshift at the wrong time though, there goes your tranny! lol Anywa on a downhill it puts more pressure on the tranny thats why the early 07 yaris stalls out when downshifting downhills. I heard about it from a friend who had a yaris.

[Hosh's One]

Originally Posted by gwasabi

If you downshift at the wrong time though, there goes your tranny! lol Anywa on a downhill it puts more pressure on the tranny thats why the early 07 yaris stalls out when downshifting downhills. I heard about it from a friend who had a yaris.

shoot..for the thing to stall out like that I would imagine it would have been red-lining or beyond for sure upon downshifting...

As far as manuals go, most of the time 4th or 5th gear is still okay on long gradual downhills...it acts like a brake, doesn't sustain high RPM's (which won't mess with your tranny) and you use the brakes ever so often...and if it happens to be steep enough to downshift into a lower gear (like 2nd) than you are most likely not going fast enough to worry about the brakes as much...just "pump" em rather than hold em down for long periods of time.

And what kinda sustained RPM's are we talking about as far as "wrecking" the tranny?

I dunno...just my thoughts...

[AlexNet0]

Well then My tranny must be made of super duper materials, because I have relied on engine braking very heavily ever since I got the car 2 years and 63k and change ago

[BluYrs]

I also downshift downhill, but the thing is that the 1.0 engine can't really slow the car down enough. So I also have to use the brakes. I also use downshifting when coasting towards a red light, it's become a habit.

As said, DFCO ftw!

[reesesyum]

Let me try and clear up a few things after reading the replies (and thanks for the replies BTW)

Of course it's better for the engine brake to slow the car going downhill - as a general rule I try to use my brakes as little as possible no matter what the condition. Due to traffic or other conditions, sometimes you have to touch the brakes a little going downhill - and this is when the gear shifts down.

This doesn't help the engine brake. As another poster pointed out - the downshift does not significantly slow the car down. It continues at the same speed, just with higher RPMs.

I also disagree that this isn't bad for the transmission. As other posts state, this is putting additional, unnecessary stress on the transmission.

There is also the problem of performance if you want to then pick up speed after the downshift. This is like trying to pedal faster going downhill when you're in the lowest gear on your bike - nothing happens.

What I find curious about this is that if you depress the brakes more fully, but still short of a full stop - due to an unexpected slowing in front of you for example- the trans does not downshift. The downshifting only occurs on relatively light application of the brakes - which in my previous driving has been a fairly common occurrence. I just find the whole thing curious.

I love the Yaris, but if this was intentional, it is one feature I could do without.

[supmet]

Originally Posted by reesesyum

This doesn't help the engine brake. As another poster pointed out - the downshift does not significantly slow the car down. It continues at the same speed, just with higher RPMs.

It may not seem significant on steep hills, but it is definitely helping you.

Originally Posted by reesesyum

I also disagree that this isn't bad for the transmission. As other posts state, this is putting additional, unnecessary stress on the transmission.

As others have pointed out, they have been downshifting on hills for 10s of thousands of miles. It does stress the engine and transmission some, but by the time you notice any wear, you will have saved 10 or so brake changes.

Originally Posted by reesesyum

There is also the problem of performance if you want to then pick up speed after the downshift. This is like trying to pedal faster going downhill when you're in the lowest gear on your bike - nothing happens.

If you're trying to pick up speed why are you braking? With the auto I can downshift into 3 going down a hill to maintain speed, and still have plenty of power to motor around people.. I'm not sure I get what you're worried about here

Originally Posted by reesesyum

What I find curious about this is that if you depress the brakes more fully, but still short of a full stop - due to an unexpected slowing in front of you for example- the trans does not downshift. The downshifting only occurs on relatively light application of the brakes - which in my previous driving has been a fairly common occurrence. I just find the whole thing curious.

I'm guessing on emergency braking you are slowing too fast for the synchros to catch

[reesesyum]

Originally Posted by supmet

If you're trying to pick up speed why are you braking? With the auto I can downshift into 3 going down a hill to maintain speed, and still have plenty of power to motor around people.. I'm not sure I get what you're worried about here

Not worried, but it definitely zaps power. I think my bike analogy holds. Occasionally you'll want to pick up speed after braking going downhill. I live in Los Angeles, and there's traffic. Going downhill, some unnecessarily brake, causing you to (lightly) brake to slow down. The engine then rears when the auto downshifts. Then you maneuver around them and want to pick up speed - but there's less power because you're in a lower gear.

Originally Posted by supmet

I'm guessing on emergency braking you are slowing too fast for the synchros to catch

When I emergency brake - I certainly don't brake slowly. The slow braking comes from non-emergency braking. Lightly applying the brakes to slow down a little causes the downshift. Emergency braking when fully applying the brakes does not cause the trans to downshift, though in that case you're coming close to a full stop, so that would be expected/unnoticed/irrelevant.