Understanding Downhill Shifting?

[MaddoxPics]

I've seen this discussed a few times with the older generations, and I'm not sure if much has changed between then in now, but wanted some clarification on what I should be doing when going down mountain passes.

I used to own a CR-V so the only options I had was S and L, both of which were practically useless as far as I could tell as I never noticed a difference with the two when I would go downhill. Maybe L I could see a slight difference, but nothing to the point of helping.

Yesterday in Sonora Pass I was doing the downshifting and leaving it around 2-3 depending on the area to help control. The issue I'd run into with both is as it would cost it would eventually start to rise in RPM (obviously). Once it hit the 3K range I would change to 3rd or 4th, but obviously that would speed me up and require me to use more brakes.

What's the best way to do this? I'm still learning and don't want to hurt the motor or transmission. Am I doing it correct and in some areas I'm just going to have to use the brakes regardless of what I'm in?

I know Sonora Pass has 26% grades so I'm sure that has something to do with it, but I'd just like a better clarification from those of you who do this all the time on what I should be doing in these situations.

 

[flyrv9]

Does the manual say anything about this?

 

[MaddoxPics]

I know I can "RTFM," but I don't have it sitting next to me at the moment and won't for awhile. The online one apparently is down.

 

[Jetboy]

It's quite different from your Honda. Honda automatics do not have the ability to downshift and hold a gear down a hill (at least most pre 2010 models). There are some steep roads that Honda vehicles are not allowed on because of this. Toyota automatics are both stronger internally and designed differently so they do have the ability to do so. Don't over-rev your engine, but you are certainly able to use an appropriate gear to assist your brakes down hills. On long downhill grades it's much better to use engine braking for safety reasons.

 

[MaddoxPics]

It's quite different from your Honda. Honda automatics do not have the ability to downshift and hold a gear down a hill (at least most pre 2010 models). There are some steep roads that Honda vehicles are not allowed on because of this. Toyota automatics are both stronger internally and designed differently so they do have the ability to do so. Don't over-rev your engine, but you are certainly able to use an appropriate gear to assist your brakes down hills. On long downhill grades it's much better to use engine braking for safety reasons.

So what's the safest RPM for the long downhill descents? Was I going to far at 3? Or as long as I'm not approaching redline areas I'm okay?

 

[TEujunga]

I would think this is one of those areas for which there is no hard and fast rule, just common sense and personal preference.

At one end of the spectrum you'll have people who tell you that brakes are cheaper to repair than transmissions and that you should NEVER downshift on descending grades.

At the other end are those who are paranoid about overheating their brakes and will downshift to the lowest gear possible in order to avoid having to use them, even on short stretches.

As is usually the case with such matters, there's a happy medium -- and where that medium lies on the spectrum is entirely up to you.

For me personally, I'll downshift a gear or two on extended downhill grades to save the brakes from overheating, but over about 3,500 RPM I'll give in and use more braking if only to save my ears from the engine din.

 

[emmantik]

From what I've noticed, downhill assist control kicks in when you are in D and you step on the brakes going downhill. It makes a similar sound similar to downshifting in S.

Depending on the slope, I will also shift down one or two gears to prevent excessive braking.

 

[Jetboy]

So what's the safest RPM for the long downhill descents? Was I going to far at 3? Or as long as I'm not approaching redline areas I'm okay?

IMO - as long as you're below redline you're not going to hurt anything. But... I would try to keep it below 3500ish and use a mix of brakes and engine if you were going much over that.

Also FWIW - It physically won't let you down shift if it will over-rev the engine. You'll get a beep and no shift.

 

[jwkilgore]

As is usually the case with such matters, there's a happy medium -- and where that medium lies on the spectrum is entirely up to you.

This.... downshift a few gears, and if the grade is so steep you're still reving up apply the brakes. Keep the revs reasonable and you won't do any damage to the transmission or engine but you'll add considerable life to your brakes and rotors.

 

[MaddoxPics]

Thanks for the replies. Seems like I was in the right ballpark, but rather be safe than sorry. Appreciate all the answers.

 

[Jeremy556]

At one end of the spectrum you'll have people who tell you that brakes are cheaper to repair than transmissions and that you should NEVER downshift on descending grades.

Those people don't understand how engines and transmissions work.

You just need to keep the RPMs below redline. The transmission won't let you downshift to a gear that would put you above redline, but I don't think there is any safety mechanism that would prevent you from exceeding redline if you were on a very, very steep incline.

 

[Jeremy556]

It's quite different from your Honda. Honda automatics do not have the ability to downshift and hold a gear down a hill (at least most pre 2010 models). There are some steep roads that Honda vehicles are not allowed on because of this. Toyota automatics are both stronger internally and designed differently so they do have the ability to do so. Don't over-rev your engine, but you are certainly able to use an appropriate gear to assist your brakes down hills. On long downhill grades it's much better to use engine braking for safety reasons.

My 2005 Accord does. I use 3rd gear coming down most of the passes on I70. What sucks is it has no way of selecting 4th gear, it is 5th gear or 3rd gear.

 

[JSparky]

I think you're fine, sounds exactly like how I manage it as well. For others who don't know, Sonora Pass is incredibly steep, especially eastbound, so either way you're going to be heating those brakes up a bit.. engine brake helps a lot here.

I typically only downshift in automatics for scenarios just like that but hesitate to do it if the grade isn't steep enough to burn up my brakes.. I'd rather replace pads more often than than deal with premature transmission issues.

I didn't know the pass was even open yet, how much snow was up there? Might have to take a trip out there soon!

 

[SATSTRAIL]

Those people don't understand how engines and transmissions work.

You just need to keep the RPMs below redline. The transmission won't let you downshift to a gear that would put you above redline, but I don't think there is any safety mechanism that would prevent you from exceeding redline if you were on a very, very steep incline.

There is. It's called a rev limiter. Every modern day vehicle has this programming in the ecm. However, it's not a good idea to just let it sit there and bounce off the rev limiter...hit the brakes and bring it down. Typically a lower gear will hold the vehicle at the proper speed and proper revs and you will never get close to the rev limiter.

 

[SATSTRAIL]

It's quite different from your Honda. Honda automatics do not have the ability to downshift and hold a gear down a hill (at least most pre 2010 models). There are some steep roads that Honda vehicles are not allowed on because of this.

Just curious… Where did you get this?… :noidea: especially the part that Hondas are not allowed on certain roads? I've never seen a single road that says Hondas are not allowed… ( or any other specific brand of vehicle for that matter) I have an 08 Honda and I use the transmission to downshift on steep descents and it works perfectly…

 

[MaddoxPics]

I think you're fine, sounds exactly like how I manage it as well. For others who don't know, Sonora Pass is incredibly steep, especially eastbound, so either way you're going to be heating those brakes up a bit.. engine brake helps a lot here.

I typically only downshift in automatics for scenarios just like that but hesitate to do it if the grade isn't steep enough to burn up my brakes.. I'd rather replace pads more often than than deal with premature transmission issues.

I didn't know the pass was even open yet, how much snow was up there? Might have to take a trip out there soon!

It opened up this past Tuesday. It was supposed to open the Friday before that, but that one snow storm came through and kept it closed a little longer.

At the pass there's a good 15ft high snow walls. As far as regular depth I'm not sure, but I'd guess at least 5-7ft. I'm sure this heatwave is helping things melt up there. The river was flooding when I was there and a section of the road was probably a good 3-4 inches under water. I would assume it's only going to get worse the next two days.

It's quite beautiful up there. It was 104 here in Fresno and at the Pass it was 50.

 

[JSparky]

It opened up this past Tuesday. It was supposed to open the Friday before that, but that one snow storm came through and kept it closed a little longer.

At the pass there's a good 15ft high snow walls. As far as regular depth I'm not sure, but I'd guess at least 5-7ft. I'm sure this heatwave is helping things melt up there. The river was flooding when I was there and a section of the road was probably a good 3-4 inches under water. I would assume it's only going to get worse the next two days.

It's quite beautiful up there. It was 104 here in Fresno and at the Pass it was 50.

Awesome, thanks for the repor. Definitely going to be interesting with the snow melt this year. I've be itching to get back Emigrant, we'll see what happens but it maybe September before anyone can get in there.

 

[(none)]

I've seen this discussed a few times with the older generations, and I'm not sure if much has changed between then in now, but wanted some clarification on what I should be doing when going down mountain passes.

I used to own a CR-V so the only options I had was S and L, both of which were practically useless as far as I could tell as I never noticed a difference with the two when I would go downhill. Maybe L I could see a slight difference, but nothing to the point of helping.

Yesterday in Sonora Pass I was doing the downshifting and leaving it around 2-3 depending on the area to help control. The issue I'd run into with both is as it would cost it would eventually start to rise in RPM (obviously). Once it hit the 3K range I would change to 3rd or 4th, but obviously that would speed me up and require me to use more brakes.

What's the best way to do this? I'm still learning and don't want to hurt the motor or transmission. Am I doing it correct and in some areas I'm just going to have to use the brakes regardless of what I'm in?

I know Sonora Pass has 26% grades so I'm sure that has something to do with it, but I'd just like a better clarification from those of you who do this all the time on what I should be doing in these situations.

As others have mentioned, keep it below the red line and you're fine. With that said, these things don't have the best engine braking because they unlock the torque converter on decal, which also creates heat...

Just curious… Where did you get this?… :noidea: especially the part that Hondas are not allowed on certain roads? I've never seen a single road that says Hondas are not allowed… ( or any other specific brand of vehicle for that matter) I have an 08 Honda and I use the transmission to downshift on steep descents and it works perfectly…

Its not a Honda thing. It's the ability to hold a lower gear for engine braking. Pikes peak has this listed as one of their requirements for access to the summit. Whether or not they actually check and enforce it, I don't know.

 

[jwkilgore]

There is. It's called a rev limiter. Every modern day vehicle has this programming in the ecm. However, it's not a good idea to just let it sit there and bounce off the rev limiter...hit the brakes and bring it down.

I may be wrong, but I don't think rev limiters work that way. I understand rev limiters to work by reducing gas/air flow and/or deactivating spark plugs. Mostly reducing air/gas flow because deactivating spark would be bad for emissions testing.

Neither of those mechanism would prevent over-rev in the case of an outside force being applied (steep grade). Again, no personal knowledge, but if I were to guess I'd say the ECU would force an upshift to protect the engine if you hit the rev limiter on a steep downhill grade while not pressing the gas.

 

[e60ral]

yeah you can't use a rev-limiter to stop an over-rev from engine braking, but i don't think that's an issue with an automatic, i assume it would just shift up or