Manually downshifting a Toyota automatic transmission harmful?

just leave it in drive normally. if im going down a big hill or offroading I'll lock my 5speed into 3rd or 4th gear. mine will downshift if you stop, but when you pick a gear it'll stay there even at redline (according to the manual, never tried it myself) engine breaking probably puts as much wear as speeding up.
 
The only reason to downshift is for descending long hills that would overheat the brakes, or brake fluid. This is the "saving the brakes" you hear about.

My dad had a 2005-ish Matrix AWD wagon. It ate a transmission by his using manual 2nd gear to descend, and properly control his car, down a 25 mph hill he lived on in Vermont. This is a known weakness of that particular transmission.

Downshifting a camry on interstate off-ramps is boy-racer stupidity.
 
My CX-5 will *automatically* downshift when going down hills, and exceeding the cruise control set speed.
I'm sure Mazda knows a hell of a lot more than internet forum posters.
 
People actually do this? :unsure:

Nobody shifts their automatics manually even with tiptronics that are designed for shifting manually :D
 
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I have paddle shifters on both of my Camry's. I just bump it down a gear or two coming down a hill to control my speed. Otherwise I just let it do its thing. My wife was trying to adjust the controls on something running down the highway and bumped it down until it was trying to run down the road on the rev limiter and couldn't figure out why her car was bogging down while I was on the phone with her.
I'll bump it down to second gear with the traction control off when driving in the snow sometimes.
 
I always liked to bump down my truck before hitting a hill that I knew it'd downshift on anyhow--liked to think it'd save on some wear and tear, downshifting when not under load--was not sure just how much communication there was between engine controller and transmission controller. Pretty sure anything 2000+ is going to be on the hard side to damage, but, who knows. At 180k you get into the area where it's hard to tell apart regular wear from accelerated wear from a change in habits, IMO.

Pure swag on my part: putting your foot in it and having it upshift under load is probably harder on parts than downshifting under low load. I mean, throttle shut, force a downshift, you get engine braking (negative power output?) but it's not equal to the power that the engine makes under WOT. Put your foot into it and let it bang shift at 5k+? as opposed to downshift when it's at 2k or whatever? Probably different parts taking different wear, but it just seems to me that upshifts are going to be where the wear occurs.

[Ok, I recall Clinebarger talking about 4L60's and how going in and out of OD is hard on the transmission, but that sounds like something that is very transmission design specific.]

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What's the difference between commanding downshift and stepping on the throttle harder so as to force a downshift? Seems to me, the latter is "harder" on things than the former.
 
When I was hauling larger loads with an old automatic I would shift manually often because the truck didn’t have enough power to maintain speed in the gear “it” would select unless I floored it.

Downshifting I didn’t have to stomp on it to maintain speed uphill.

Same going downhill, I would go down a gear and reduce speed near the top of the hill and let the load accelerate me a bit so I wasn’t going 100mph at the bottom of the hill. Then I didn’t have to ride the brakes a half mile.
 
When driving our '09 Kia Sedona (5-speed automatic) in the mountains I'd have one of the readouts on the Scangauge set to LOD (load). When the indicated load hit about 80% I'd manually shift to 4th. This would happen when climbing.

The 80% was an arbitrary decision on my part - I don't know if I should have shifted sooner or whether the transmission would have downshifted on its own if I'd left it.

In any case, the van is still in the family and there have been no transmission problems to date.

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With our '97 Mazda MPV (4-speed automatic) I used to disable the OD when driving in the city. Kept the column shifter in D, but pushed the OD override button on the shifter.

No transmission problems over the time we owned the van (2001 through 2018).
 
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why do automatic trannys shift into the highest gear possible? rpm won't hurt the engine, but always lugging the engine and slipping the transmission will wear stuff out.
 
why do automatic trannys shift into the highest gear possible? rpm won't hurt the engine, but always lugging the engine and slipping the transmission will wear stuff out.


They do what the computer tells them. Fuel economy is the top reason. Why do you want to keep the engine at high rpm?
 
why do automatic trannys shift into the highest gear possible? rpm won't hurt the engine, but always lugging the engine and slipping the transmission will wear stuff out.
*puts on tin foil hat* Why would you think the OEM would want your car to last? Faster to wear out, faster you’ll buy another, right?

Tin foil hattery aside, quick upshifts only bother those who plan to roll into the throttle. Most are sedately driving and a quick upshift keeps rpm’s low, for mpg, and possibly keeps NVH low, for smoother ride.
 
i don't usually want high rpm, but for example when I climb a hill in an automatic i gradually give it more gas to maintain speed, and the stupid transmissions won't downshift until ive reached like 3/4 throttle and the engine is below 1500 rpm. cars with more torque don't bog so much, but In my car there's not much power below 2500 rpm. i usually manually downshift for big hills. automatic transmissions just seem to avoid downshift, which is fine for cruising around town but annoying offroad or in the mountains. i guess many people just stay in town though
 
*puts on tin foil hat* Why would you think the OEM would want your car to last? Faster to wear out, faster you’ll buy another, right?

Tin foil hattery aside, quick upshifts only bother those who plan to roll into the throttle. Most are sedately driving and a quick upshift keeps rpm’s low, for mpg, and possibly keeps NVH low, for smoother ride.
that's true, sticking it in the highest gear possible does make for a smooth and quiet ride.
 
Have you ever tried turning an engine backwards using the crankshaft snout/bolt and observe what the timing belt tensioner does?
If not, you’ll never understand.
When the engine is used for slowing the car there is a situation created where the timing belt tensioner can back off tension.
 
But have we seen cases where the cam sprocket got loose? no, we see TB failures from neglect. Old belts or failed rollers.
 
Have you ever tried turning an engine backwards using the crankshaft snout/bolt and observe what the timing belt tensioner does?
If not, you’ll never understand.

Yes, I have. And what does that have to do with using the engine to slow the car? Is the engine suddenly turning backwards?

The timing belt is pulled by the crankshaft sprocket. If the engine is running, the timing belt is being pulled. Forward. In no case is the engine going to be rotating in the opposite direction while it is running, whether it is spinning because of combustion acting on the pistons and connecting rods, or being driven by the wheels through the axles and transmission. The rotation of the engine does not reverse when you are coasting or using the engine to slow the vehicle.

When the engine is used for slowing the car there is a situation created where the timing belt tensioner can back off tension.
By all means, please describe how this happens.
 
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Yes, I have. And what does that have to do with using the engine to slow the car? Is the engine suddenly turning backwards?

The timing belt is pulled by the crankshaft sprocket. If the engine is running, the timing belt is being pulled. Forward. In no case is the engine going to be rotating in the opposite direction while it is running, whether it is spinning because of combustion acting on the pistons and connecting rods, or being driven by the wheels through the axles and transmission. The rotation of the engine does not reverse when you are coasting or using the engine to slow the vehicle.


By all means, please describe how this happens.
 
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