Manually downshifting a Toyota automatic transmission harmful?

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Jun 15, 2021
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Folks,

I have a 2009 Toyota Camry 4 cylinder with automatic transmission. It has 180,000 trouble free miles and used to be my wife’s daily driver before she got a newer car. It is now my winter car.

The transmission shifter was for the first 179,000 miles simply placed in “D” and the car was driven as a normal automatic transmission sedan… as I suppose most commuter cars are.

One can however manually move the shifter from “D” to “4” to “3” to “2” and even to “L”.

When I drove a manual transmission, I would always downshift when approaching interstate exits or stop signs, or slowing traffic… I believed it saved wear on the brakes to use the manual transmission to slow the car. But that was a true manual with a clutch.

My question is – given that the transmission has 180,000 miles on it – and to be truthful it is an automatic transmission with the “ability” to be shifted by hand… and I hurting it by doing so? I never exceed 3500 RPM, and never go lower than “3”, but I can drop from 70mph to 40mph exiting the interstate without braking.

I am most concerned about keeping the transmission happy for another 50K, and if I should leave the transmission in “D” and just use the brakes, I am willing to do so… however if downshifting is not hurting anything, I prefer to do that.

What says the brain trust? Thanks in advance!
 
Engine braking is illegal in my town. LOL

I'd just leave it in D and relax. I only downshift on this one road in Princeton, NJ that is downhill and has a 25 mph speed limit and I have to keep riding the brakes to keep close to the speed limit.
 
I've manually shifted automatic transmissions since driving them in the 60's. Also have overhauled many of them. Its not going to hurt a thing, even the old owners manuals used to suggest down shifting them on steep hills, especially for trucks. And some truck automatic transmissions even had a built in hydraulic retarder, that sort of works like a small fluid coupling to slow the vehicle down.
There is a reason I can get around 70,000 miles on a set of brakes, just standard ones that are nothing special.
 
With 180,000 trouble free miles driven in D I would not change it now.

It has always been my seat of the pants observation that cars adapt to the habits of the common driver and transmissions especially don’t like change. I swear that the few time that I have loaned my car to my buddy for a week or so when he had car issues that when I got it back it drove funny, shifts were in the wrong place and gear changes were not smooth like they had been. It took a week or more for me, or perhaps the car, to readapt to each other.

If it ain’t broke don’t fix it!
 
I suspect that’s only for large trucks with unmuffled Jake brakes.
For sure, that is why the law exists but I'm not sure if there are exemptions for passenger vehicles. Not that I think the police will bring in a Camry driver for downshifting. That would be funny.
 
Thanks for the replies thus far...

Would I be correct in assuming that those of you who are saying to keep it in "D" and use the brakes are implying that I am somehow damaging the transmission by forcing downshifts to slow the car?

In the alternative, if there is no harm to the transmission, I am increasing the life of the brakes by so downshifting, which is a net gain for me...

The crux of the question is: Am I doing any harm to the engine or transmission?
 
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A lot of ninny’s in this place.

1. Most Modern Automatic cars won’t allow you to overrev even if you shift to 1 (you don’t have a 2001 Dodge Ram do you?). And if your car does allow overreving, use your brain to select an appropriate gear for the speed.

2. Automatic transmissions are designed to shift, if they fail during a downshift they are a piece of garbage that will fail anyway.

3. Antique versions of your car had a 2 or 3 speed and the engine cruised at the RPMs your worried about on the highway or while accelerating.

The only way I could see what you describe as being even close to an issue is if your car is already not operating correctly and you decide to descend a long mountain downgrade in first near redline .

I would trade not crashing for excess engine wear going down a mountain thought.

I guess folks here love brake fade going down the beartooth
 
Thanks for the replies thus far...

Would I be correct in assuming that those of you who are saying to keep it in "D" and use the brakes are implying that I am somehow damaging the transmission by forcing downshifts to slow the car?

In the alternative, if there is no harm to the transmission, I am increasing the life of the brakes by so downshifting, which is a net gain for me...

The crux of the question is: Am I doing any harm to the engine or transmission?
You've got a 14 year old car with 180,000 miles. The question that you should be asking yourself is why would I unnecessarily tax an older and expensive drivetrain over cheaper and easily replaceable brake parts?

In the end it's your car. Drive it the way that makes you happy.
 
... The crux of the question is: Am I doing any harm to the engine or transmission?
As long as you keep the engine in its normal RPM range (below redline), then no, you shouldn't be.
To slow down, you need to convert kinetic energy into heat. The brakes and engine can both convert excess energy into heat, and both are designed to do it efficiently.
Any engine or transmission that fails or is damaged by downshifting is poorly engineered or built. Downshifting is normal operating / driving procedure, for both automatic & manual transmissions.
 
You won’t be causing damage if done right. Is it worth it ?

There might be specific situations where a manual mode can work. A long grade for example.

I would just leave it in D and go. If the situation dictates you need to manually choose a gear then go for it.
 
Leave it in D, downshift for downhills only - and maybe on snow and ice to keep the trans in a limited shift range to maintain speed/control. Definitely shift to 2/1/L in 4WD LO to climb or crawl if it’s a truck.

The “numbers” are the max gear the trans will shift to, many will not manually “shift” and lock to a selected gear. For example, PRND4321, D means all the gears including overdrive are available, 4-1 means it will be limited up to that gear. Older Japanese cars used a PRND2L, 2 limits shifts to 2nd gear and L is locked to 1st gear. Ford and GM would have the D in a circle with an O/D OFF button.

Some automatics can be shifted like a manual via paddle shifters - the Lexus 8/10 speeds in the F cars/LC500 and the Mercedes-AMG SpeedShift are examples of such.
 
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