I was listening to the show last week and I just wanted an explanation on one of the callers questions. The caller was saying she was driving down a hill with her manual car accidentally in neutral and by the time she has gotten down to the bottom she had burned her brakes.The hosts then tell her that she shouldn’t have done that and next time the car should be in 1st or 2nd when going down the hill. They also mentioned that though the engine might be “screaming” when going down the hill in 1st or 2nd, it is the right thing to do. I think what they said was that as long as the engine isn’t redlining then it is okay. What I don’t understand is why the engine would be “screaming”. Can someone please explain to what exactly is going in with the engine when you put your tranny into 1st/2nd gear and go down a steep hill? Where does the "screaming"engine come into the picture? I’m assuming that when they said “screaming” they mean that the engine is running real fast.
Having trained mountain school bus drivers here in Colorado my recommendation is to be in the same gear going down hill as you would use going up hill. True for either manual or automatic transmissions. If you engine is reving too high, tap the brakes on occasion, but do not ride them. Most passenger vehicles are light enough that engine compression will hold a reasonable speed. Four-wheeling down steep logging roads is another story.
What causes the engine to rev up? I thought the engine speed is controlled by the speed on transmission so as long as your transmission is set to a low gear wont the engine just run at a slow speed? PLease correct me if I am not understanding this correctly.
I would have felt we were dealing with an issue of substance if the person in the story said her brake were fading, with “burnt” you dont know what degree the problem is. You have to look long and hard these days to find a downhill that will burn or even make the brakes fade.There is not one in many miles from where I live and we have a 10 mile long 6% grade nearby. It does not affect the brakes on my 2004 F-150 at all.
Now the 60’s and 4 wheel drums with a trailer in the Sierra Nevadas, now we have a senario where special technique needs tobe used.
Gravity. The car wants to roll downhill, but if the car is in gear it has to turn the engine too. Since it takes energy for the pistons to compress air in the cylinders, the engine slows the car down.
A “low” gear provides the fewest drive wheel rotations relative to engine rotations and makes it easy for the engine to move the car. But when you’re engine braking, the drive wheels are turning the engine and so the “low” gear becomes high-- 1st gear makes it hard for the weight of the car rolling downhill to turn the engine, but it also provides the most engine rotations per drivewheel rotation. So if you’re creeping down a hill, you want it in a low gear so it’s as hard as possible for the car to turn the engine (thus providing the maximum engine braking), but it also means that there is a high number of engine rotations per drivewheel rotations, hence the screaming engine.
I’m sure there’s a more succinct way of explaining that, but it’ll do for now.
In general, immediate braking is best done by your brakes while sustained braking by the engine/transmission. Both are necessary and situational. Down shift early enough while speeds are moderate and avoid the screaming motor.
A 6% grade barely qualifies as “downhill”. An out of shape person can easily climb that slant on a bicycle.
Did you notice that they didn’t use the mantra of this board, “Brakes are cheaper than transmissions” instead pointing out that riding the brakes can cause total brake failure as the fluid boils? I suggest a new mantra: “Transmissions are cheaper than slamming into something because you rode the brakes going down a hill, regardless of what people on the internet say.”
When it comes to making roads it is the max spec for many. What kind of a hole have you crawled out of to bless us with such wit?
“Read the owner’s manual” is better advice. Engine braking is in there for a reason.
I loved the Chrysler 300 rental car cruise, it did everything I needed, like no worries mate! It maintained cruise settings in the mountains and the plains, who could ask for anything more. Auto down shift etc. so simple a cave man could do it.
We’ve discussed this many times. Cars with regenerative braking (hybrids) use brakes much less and is where we all are headed. Free wheeling is not the best way to go and with computer controlled electric drive in all of our futures, the traditional brake will be regulated to parking brake only status with it’s natural energy loss. Many cars and trucks still using IC engines will automatically downshift all the time as some do already. Engine/trans are as valuable as braking components as they are “go” components. Use them that way as intended.