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Maybe someone is knowledgeable about the following scenario.
Someone I know drives on the curved hill every day. He switches to 1 in order to take advantage of the engine's "hold back" and not to apply breaks frequently.
The question is: is it ok to shift between D and 1 while in motion? Or the full stop is recommended? How bad is such practice on transmission/breaks/tires?
I'm always amazed to hear stories like this. I can imagine that it's not great for an automatic transmission to be frequently downshifted into first gear for engine braking while moving. I admit that I don't know how bad, but it's not nothing. Automatic transmissions can be fragile and are expensive to repair or replace. On the other hand, brake pads and rotors are cheap, durable, and easy to replace. It doesn't make any sense to try to save your brakes at the expense of your transmission.
I'm always amazed to hear stories like this. I can imagine that it's not great for an automatic transmission to be frequently downshifted into first gear for engine braking while moving. I admit that I don't know how bad, but it's not nothing. Automatic transmissions can be fragile and are expensive to repair or replace. On the other hand, brake pads and rotors are cheap, durable, and easy to replace. It doesn't make any sense to try to save your brakes at the expense of your transmission.
The purpose of downshifting and using engine braking instead of riding your brakes down big, steep hills is not to save the brakes from wear, but to save them from overheating and creating a dangerous situation where the car cannot be stopped.
Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
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It costs a lot more to repair a transmission than brakes, but the transmission should be able to handle that some. Compromise is best. I would not go from D to 1 on a 4-9 speed transmission. Maybe on a 3 speed or less. Better to go from D to 2 and use some engine compression and some regular brake. Modern disc brakes do not overheat and fade like the old drum brakes but the constant use down a lot of hills wears them out faster and can cause the rotors to warp, since they are getting thinner to save weight to increase MPG.
People that say it will damage the tranny somehow dont realize that they come from the factory with the ability to downshift manually....that's what it's there for. My first Subaru was an auto, and when I needed to downshift for a big hill, I did it in order. D-3, 3-2, 2-1(if needed). I didnt just yank it down straight from D to 1.
The idea is to be going the correct speed range (slow) when shifting into 1st. Then no problem. Your car automatically does this when you slow down, no difference!
I think if you are going too fast (like say 55) and try shifting into 1st, it may not let you or the transmission will not shift into 1st until you slow down enough (transmission damage prevention feature)????
I know I have had manual transmission cars and it would not let me shift into 1st if I was going too fast. (That was because I accidentally was trying to shift into 1st - also had the clutch in.)
Anyway I have not tried that with an automatic and don't recommend anyone else does either!
It must be a pretty old car to have PRNDL, and if it has lasted this long, driver abuse is clearly not a problem. Nowadays, cars are all PRND21, and if it were me, I would either let 2 address the need, or pause in 2 until I felt the effect, then go on to 1. I don't know of any hill in North America that is steep enough and long enough that one can't, with a normal load, either use the brake or 2 to maintain speed control going down. "Every day" is not often enough to constitute applying the brakes "frequently". If the hill is so steep that 1 is needed going down, and it is a front-wheel drive, I doubt if he can get back up again.
downshifting in an automatic is no problem. most automatics built after 1980 or so wont let the trans downshift into first until the road speed drops to a certain point. for instance my 84 tbird with the AOD would not drop into first until the road speed dropped below 20mph. this is to prevent the engine from over revving and being damaged.
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