Going Downhill Manual Shift...Brakes Or Tranny?

In the subdivision I live in, to exit the development you have to go down a pretty steep hill. I drive a 5-speed Scion to work every day, and to help keep my speed down going down the hill, I stay in second gear. This pulls my RPM’s up to 4,000 while doing this.

My wife was in the car recently when I did this and she was like “Oh man, you’re really going to mess up your car!”
I asked her how she went down the hill and she said she either coasts in neutral or stays in third gear, presumably riding the brakes the whole way down (which is what I am trying to avoid by staying in 2nd gear).

So the question is, is this harmful? I don’t think it is. And also, does it use more gas going downhill at a higher rpm, even though I’m not touching the throttle?

If you coast down the hill in neutral, you have to ride the brakes to keep from going around 50mph, and the speed limit is 25 in my neighborhood.

Who’s doing the more correct thing here?

You are. You have better control of your car if the engine is braking for you. The Engine doesn’t have a foot to slip off the pedal. It’s also just a good habit, on long grades, you can overheat the brakes to the point of failure. She has a minor point that it puts the stress of the braking on the tranny, rather than the brakes. But nothing it wasn’t designed to do, and if it’s safer, it’s worth the wear and tear on the tranny.

Your wife’s mechanic is going to love her.
From what you described, she is going to wear out brake pads a much faster rate than most people.
The mere fact that the engine is turning 4,000RPM is not harmful in and of itself. Down shifting to second can cause wear to the clutch, but from what you described this is not an issue here.
Coasting down a hill in neutral used to be listed in the California Driver’s Handbook as being against the law and a generally bad idea. This was back in the day when most cars had drum brakes, which would fade easily leave you with no way to stop. Now a days with front discs or 4 wheel discs, brake fade is less of a problem, but it can occur.
Leave the car in gear.

Obligatory Cecilian column

Man, there are lots of these threads…

I know, but this one in particular was aimed at dispelling the notion that it isn’t OK to let your manual shift car rev higher in a lower gear in order to safely negotiate down a steep slope.

My wife will be happy to know she’s wrong…she always is!
:smiley:

Whatever makes you think she’s going to accept she’s wrong?

Ha. She’s not going to, that was the gist of my :smiley: face.

As any married man knows, she’s always right, and on the rare occaison when she admits fault, we are supposed to shift into “It’s not that you’re really wrong, dear” mode.

If a tree falls in the middle of the woods and no one is around to hear it…is the husband still wrong???

You can be right or you can be happy.

On the fuel consumption thing, if your engine is fuel-injected then the injectors probably cut off any time the road is turning the engine, so coasting would save nothing (indeed, would use fractionally more fuel, as you need to keep the engine idling).

IMO, brakes are for stopping, not for controlling your speed. An oversimplification, but then soundbites are.

Or else the conversation shifts into one about what you’ve done wrong, including making her feel bad.

If you coast in the UK you are not considered to be in control of your vehicle, do it on your driving test and you fail (major fault).

Brakes will heat up and fail on hills, so thats a big reason not to brake all the way down a hill. OK so she didn’t go off the road when they overheated or start a fire along the road. Instead only the rotors are warped and the brake pads glazed, requiring most of the components be replaced. The above is more likely to happen than you damaging the transmission.

Aside from the brakes, isn’t it pretty hard on the bearings somewhere to coast in neutral?

No.
Unless your speed exceeds safe limits, which has nothing to do with coasting itself.

You might be thinking of the throw-out bearing in the clutch. Coasting with the stick shifted to neutral won’t hurt this, but coasting with the clutch pedal depressed the whole time will make that bearing old before its time if you do it enough.

I guess this is similar to the question of how to slow down for an intersection with a manual transmission.

Shifting down and using the engine braking feels like the cool thing to do (some of the point of having a manual I guess) but … as someone pointed out to me, clutch, gearbox and engine cost a lot more to fix or replace than brakes which are supposed to wear out. So … I tend to put it in neutral early and use the brakes.

I frequently go down a long hill which is steep in some places. I tend to compromise and stay in third gear where I would have been in fourth if it was flat and use a bit of both engine and brakes.

I guess different cars behave differently but most automatics that I’ve driven seem to give very little engine braking so I suspect that using the brakes isn’t much harder on the brakes than if it was an automatic.

Using the transmission to slow down, or regulate speed, isn’t necessarily a bad thing. Bear in mind that it’s under load the whole time anyway, as the engine must at minimum provide enough power to overcome rolling friction and air resistance, so it need not be under excessive load just because the push is, in effect, going in the other direction. Naturally it’s a bad idea for the clutch to be part in and part out, but that’s not what we’re arguing for here. I believe you’d have to be seriously savage with the engine braking to do much harm. In many tens of thousands of miles in manuals, I don’t think I ever wore out a clutch, but I’ve been through plenty of brakes, and all the more on motorbikes.

In my experience, having driven both, you notice engine braking much more with a manual than an auto. No surprise there - there isn’t a torque converter mushing everything up for you. It’s sort of the other side of how the accelerator feels much more directly connected to the wheels; in an auto, I put my foot down, the revs rise quickly, the car catches up when it’s good and ready. You don’t get that in a manual.

And you can only be happy if she’s happy. (Then it’s only a slight chance anyway! :D)

I have to agree with those on the “engine controls speed” not brakes side of this. Brakes are for stopping, and large/emergency speed control. As mentioned, on a stick, this is much more dramatic.

Your clutch won’t prematurely wear from this sort of use, as it’s designed to do exactly this.

Also, a transmission in neutral puts you in a position that takes extra time to resolve, in the event that you need to apply power to the roadway.

Going up and down hills is one of the big advantages manual gearboxes have over automatics. Its definetly better to use the gears to slow down your car.

Near where I grew up in the UK there is a pretty serious hill with a traffic light and cross-roads at bottom. At the top there is a big sign saying “Change to low gear now”, in order to avoid people relying on their brakes too much.

Everyone’s mentioning hills, how fast do you coast down them? I’ve gone down large, long grades in everything from subcompact manuals (Civics), to huge 2.5 ton manual trucks (military), and in a whole array of automatics from midsize (Fusion) to giant SUV’s (Expedition). In my experience, there’s always some type of terminal velocity that’s reached within the bounds of what’s manageable. I’ve often found myself needing to use the accelerator when going down a hill in order to avoid slowing down beyond the speed I want to travel at.

Don’t get me wrong; you have to anticipate other traffic, curves, surprises, and so on, and sometimes dropping it down a gear – in an auto or a manual – is needed prior to making a new maneuver, but barring other contributory factors that might make a situation dangerous, I question whether gravity is enough to make a situation dangerous, i.e., you just don’t go that fast.

Well there’s hills and then there’s hills. Some places in the midwest there are hills the locals will point out that I can’t even see. You’d have to get out and pour a glass of water on the road to tell if your climbing or descending. Here, not so much. My daily commute has a 4.5 mile section with 1000’ of vertical drop. The top half of that road is what I would consider a mild slope, and coasting would be possible with an occasional tap of the brake or gas. The bottom half would burn up the brakes in short order, and would be impossible to coast down safely.