Driving down a steep grade

toyota
4runner

#1

I have a commute to /from work that takes me from 2000’ to 5300’ in about ten miles. I have been putting my 4Runner into D3 on the way down to save the brakes. Is this the best thing to do?


#2

My drive also includes a drop of about 1000 feet. I see no reason to save the brakes, because new brakes are relatively cheap. New transmissions are very expensive. I would use the D3 if I was carrying a heavy load or towing or somehow at risk of losing control because the excess weight made it difficult to stop with the brakes.

Also, I use the brakes for shorter, somewhat firmer slowing, then let the speed build up again for a while. That way the heat gets to dissipate. If you keep your foot lightly on the brakes all the way down they get hotter and hotter, and never cool off. That can cause problems that limit their efficiency.


#3

You should drive down a steep grade in the same gear you went up.

Twotone


#4

I recommend at Twotone recommended with a small adjustment.

Using the brakes to slow down on a long downgrade can be dangerous. If the brakes overheat, they can fail. I does not happen often so not many of us have it happen, but it is a real safety issue if it does happen.

That said, I would suggest that there are times you should downshift when going down hill when you might not down shift going up. It depends on the grade your car, the length of the grade etc. Sometimes you may want to use both.


#5

Of course it’s OK. This constant debate about brakes being cheaper than transmissions is a false choice. You have D3 for just such driving, that’s what it’s there for and provided you don’t drive too fast and engine stays within normal operating range, go for it. It’s the gear changing and towing that wear a tranny most.
Cars are designed to brake with a combination of engine and foot brake, both used in accordance with the manual…and the manual and Toyota service manager say it’s fine.


#6

If downshifting a transmission is bad, then I don’t understand why some cars would downshift while going downhill automatically. Failing transmissions do not do well for an automobile manufacturer’s reputation. And yet, engineers are confident enough to program a transmission to downshift.


#7

THanks to all for your replies.
I don’t fly down the mountain, I like to just follow the curves without having to break at every one, (I certainly go up faster than I come down). Seems that being in D3 allows me to keep a better, smoother pace because I’m not racing the engine. I definately feel safer when I’m in snow: 4WD and the lower gear gives more control.


#8

4WD and a lower gear will NOT give you more control going downhill in the snow. Maintaining a reasonable speed and having four suitable tires is what does that! There are times in the snow (especially on a downhill) when being in a lower gear can actually hinder control.


#9

I fully agree. On ice especially and wet snow that clogs the treads it’s best to nearly “free wheel” and use the abs brakes as needed. The reason is that any wheel being braked or accelerated in general has less traction for steering and tracking. Starting out slow and not having to brake too much is important.
We really enjoy our 4Runner too.


#10

Going downhill isn’t going to stress you transmission any more than going uphill. Why would it? I’m sure someone will tell me where I’m wrong, but I’m not sure I’ll be buying it.


#11

I do exactly what the OP does when faced with his situation. In addition, I will also turn on the air conditioner for extra braking even when I don’t need AC.


#12

That’s a “cool” idea !


#13

The same amount of heat energy is created both ways (unless you are dragging without slowing). More pressure for shorter bursts causes more heat to be transferred in less time, so they have to cool more, so the net effect is similar. Heat sinks do operate more efficiently the hotter they get, but the difference is not as much as you may think.