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ChevyMan
05-08-2007, 03:54 PM
I have a bad (is it really ?) habit of shifting from D to L2 when going down a slight inclination of the highway..35MPH..with traffic signals at the bottom of the hill. The incline is steep enough for the car to reach 45 even in D so I hate to use my brakes when the lights changes, but in L2 gear the tranny will not go over 25 MPH thus easier on the brakes.

My question is: Will this action do any damages to the transmission? What do all think??

Kwozzie1
05-09-2007, 07:58 AM
I have a bad (is it really ?) habit of shifting from D to L2 when going down a slight inclination of the highway..35MPH..with traffic signals at the bottom of the hill. The incline is steep enough for the car to reach 45 even in D so I hate to use my brakes when the lights changes, but in L2 gear the tranny will not go over 25 MPH thus easier on the brakes.

My question is: Will this action do any damages to the transmission? What do all think??


I do the same......don't think it does any harm

Eric
05-09-2007, 08:31 AM
I have a bad (is it really ?) habit of shifting from D to L2 when going down a slight inclination of the highway..35MPH..with traffic signals at the bottom of the hill. The incline is steep enough for the car to reach 45 even in D so I hate to use my brakes when the lights changes, but in L2 gear the tranny will not go over 25 MPH thus easier on the brakes.

My question is: Will this action do any damages to the transmission? What do all think??


Brake pads are cheap and easy to replace. A transmission is neither. Why put the extra stress on your transmission?

DonTom
05-09-2007, 09:20 AM
"My question is: Will this action do any damages to the transmission?"

If the RPM's get too high, you can blow the engine going downhill. A piston rod broke in my RV while going downhill in the mountains while in second gear.

IMO, it's better to wear out your brakes.

-Don-

Eric
05-09-2007, 09:22 AM
"My question is: Will this action do any damages to the transmission?"

If the RPM's get too high, you can blow the engine going downhill. A piston rod broke in my RV while going downhill in the mountains while in second gear.

IMO, it's better to wear out your brakes.

-Don-




Amen - I said the same....

DonTom
05-09-2007, 10:04 AM
No question here, just a comment . . .

Looks like I have to fix my Saturn today. My alternator idiot light is on with the engine running. This was just before I left for work, so I had no time to take a closer look. Drove my pickup to work today. I am at "work" now and get off in about an hour.

Unfortunately, in this car (1996 Saturn) the alternator is down very low on the serpentine belt and can only be accessed from under the car. And I don't think it's in the clear. I will have it on the ramps later today, as well as look in my many shop manuals. I meant to bring the manuals to work, but I forgot them.

-Don-

Eric
05-09-2007, 10:14 AM
No question here, just a comment . . .

Looks like I have to fix my Saturn today. My alternator idiot light is on with the engine running. This was just before I left for work, so I had no time to take a closer look. Drove my pickup to work today. I am at "work" now and get off in about an hour.

Unfortunately, in this car (1996 Saturn) the alternator is down very low on the serpentine belt and can only be accessed from under the car. And I don't think it's in the clear. I will have it on the ramps later today, as well as look in my many shop manuals. I meant to bring the manuals to work, but I forgot them.

-Don-


Sounds fun! (Don't you love modern engine compartments and engine "packaging"?)

I can get the alternator off my Trans-Am in less than 5 minutes using a 9/16 wrench to remove two bolts. Just one electrical plug-in. That's it; easy peasy Japaneesy!

TC
05-09-2007, 03:21 PM
I have a bad (is it really ?) habit of shifting from D to L2 when going down a slight inclination of the highway..35MPH..with traffic signals at the bottom of the hill. The incline is steep enough for the car to reach 45 even in D so I hate to use my brakes when the lights changes, but in L2 gear the tranny will not go over 25 MPH thus easier on the brakes.

My question is: Will this action do any damages to the transmission? What do all think??


I think you are doing the correct thing.
Otherwise, what would happen if your brakes were to fail.

Eric
05-09-2007, 03:54 PM
I have a bad (is it really ?) habit of shifting from D to L2 when going down a slight inclination of the highway..35MPH..with traffic signals at the bottom of the hill. The incline is steep enough for the car to reach 45 even in D so I hate to use my brakes when the lights changes, but in L2 gear the tranny will not go over 25 MPH thus easier on the brakes.

My question is: Will this action do any damages to the transmission? What do all think??


I think you are doing the correct thing.
Otherwise, what would happen if your brakes were to fail.


I doubt there is any danger of the brakes failing under such conditions (unless they are in poor condition to begin with).
It takes prolonged, heavy (and usually, repeated) braking to get to the point where brakes fade, let alone fail. Such situations are rarely encountered in a passenger car, under anything like normal driving conditions. A mild grade such as Chevyman describes should not pose a problem. So given that, I'd rather use the brakes for their intended purpose than put additional strain on the transmission by gearing down (which may result in excessive heat build-up/premature wear, etc.).

As I wrote previously - brake pads are cheap and easy to replace. A transmission is neither!

TC
05-09-2007, 04:34 PM
I doubt there is any danger of the brakes failing under such conditions (unless they are in poor condition to begin with).
It takes prolonged, heavy (and usually, repeated) braking to get to the point where brakes fade, let alone fail. Such situations are rarely encountered in a passenger car, under anything like normal driving conditions. A mild grade such as Chevyman describes should not pose a problem. So given that, I'd rather use the brakes for their intended purpose than put additional strain on the transmission by gearing down (which may result in excessive heat build-up/premature wear, etc.).

As I wrote previously - brake pads are cheap and easy to replace. A transmission is neither!



Would you recommend the same behavior with a manual transmission?

Eric
05-09-2007, 06:40 PM
I doubt there is any danger of the brakes failing under such conditions (unless they are in poor condition to begin with).
It takes prolonged, heavy (and usually, repeated) braking to get to the point where brakes fade, let alone fail. Such situations are rarely encountered in a passenger car, under anything like normal driving conditions. A mild grade such as Chevyman describes should not pose a problem. So given that, I'd rather use the brakes for their intended purpose than put additional strain on the transmission by gearing down (which may result in excessive heat build-up/premature wear, etc.).

As I wrote previously - brake pads are cheap and easy to replace. A transmission is neither!



Would you recommend the same behavior with a manual transmission?


If it's a "forced downshift," yes.

With the automatic, in Drive, the transmission knows what gear is right for a given condition; forcing it into a lower gear than it would otherwise be in for purposes of engine braking may be smart on a long downhill stretch - where constant brake application might lead to brake fade) but given the conditions Chev related, I think it's not necessary - and puts extra strain on the (expensive) transmission in order to save the (cheap) brake pads/shoes, etc.

Just my 50 cents...

ChevyMan
05-09-2007, 11:07 PM
I've gotten some cons and some pros on this issue of using the lower gear so I'm still somewhat uncertain as to whether I should continue doing the way I'm doing it or not. If you must know, the roadway is only less than quarter mile distance from the top of the grade to the signalized intersecton and I do tap on the brakes occasionally to aid the engine's braking. Am I making any sense? I've been doing this for a very long time and so far nothing negative have happened. You are always advised to use the lowest gear depending on the steepness of the incline to save on brake lining wear.

I'm hoping to hear others' opinion on this matter.

DonTom
05-10-2007, 07:35 AM
"Would you recommend the same behavior with a manual transmission?"

I prefer a stick shift in the hills especially for that reason. It's easier on the brakes and it doesn't roll downhill nearly as fast as an automatic when it's in the normal gear for the wanted downhill speed.

-Don-

Eric
05-10-2007, 07:51 AM
I've gotten some cons and some pros on this issue of using the lower gear so I'm still somewhat uncertain as to whether I should continue doing the way I'm doing it or not. If you must know, the roadway is only less than quarter mile distance from the top of the grade to the signalized intersecton and I do tap on the brakes occasionally to aid the engine's braking. Am I making any sense? I've been doing this for a very long time and so far nothing negative have happened. You are always advised to use the lowest gear depending on the steepness of the incline to save on brake lining wear.

I'm hoping to hear others' opinion on this matter.


Well, as I wrote earlier, the primary purpose of your brake system is to slow the car down. It's ok to use the brakes for the work they were designed to do. Now, in certain situations - such as a long downhill grade, where it's possible that prolonged use of the brakes may lead to fading, etc. - it's fine to "gear down" and use the effect of engine braking to slow the vehicle without over-taxing the brakes.

But the situation you've described is not that extreme; just a short downhill stretch. I doubt you're doing any damage - but why "save" the (cheap, easy to replace) brake shoes/pads at the expense of your transmission? You're making it work harder, unnecessarily, etc.

Eric
05-10-2007, 07:56 AM
"Would you recommend the same behavior with a manual transmission?"

I prefer a stick shift in the hills especially for that reason. It's easier on the brakes and it doesn't roll downhill nearly as fast as an automatic when it's in the normal gear for the wanted downhill speed.

-Don-




And also, a manual gearbox needs the driver to select the appropriate gear for a given road speed/condition - whereas an automatic uses line pressure/throttle position, etc. to "self-select" the correct gear at any given time. When you move out of "Drive" you are over-riding the automatic's "choice," etc. It's usually not necessary to do so.

And automatics use fluid under pressure to transfer power (unlike manuals, which use a direct mechanical connection via the flywheel/clutch straight to the gears, etc.). The harder you "work" the automatic, the hotter the hydraulic fluid gets - and the hotter it gets the faster that fluid (and its additives) break down. High heat is a killer for automatics; it's basically a non-issue for a manual gearbox....

DonTom
05-10-2007, 08:05 AM
"Sounds fun! (Don't you love modern engine compartments and engine "packaging"?)

]I can get the alternator off my Trans-Am in less than 5 minutes using a 9/16 wrench to remove two bolts. Just one electrical plug-in. That's it; easy peasy Japaneesy! "

It really depends on the vehicle. I could do a very fast alternator change in my 1988 Biretta (2.8L) that I used to own before the timing chain broke. About one minute to remove the serpentine belt and another minute or two to replace the alternator and put the belt back on. But it was in the clear, alternator on the very top of the serpentine belt.

The Saturn puts the alternator on the bottom of the belt, with countless things in the way. I discovered today that I cannot use ramps because the right front wheel has to be removed along with all the fenderwell splash shield garbage. A 9/16" or 14 MM box wrench can remove the serpentine belt if it's long enough. A serpentine belt tool should work too, but I left it in my Jeep that's at the other home. I will buy another one of these later today. If I cannot find such here, an extra long 9/16" or 14 MM box wrench will do. It has to be long enough for some good leverage. I will have to work with the vehicle on jackstands.

I have replaced many alternators before, but by far, this is the toughest one of all. I only looked at the vehicle yestarday and got some things ready for this job. I purchased the alternator yesterday (Wednesday) too. Perhaps today I will complete the job, but Tom & I do have some other plans. Having so many vehicles means fixing this one is no big emergency.

-Don-

Dave Brand
05-10-2007, 09:06 AM
Now, in certain situations - such as a long downhill grade, where it's possible that prolonged use of the brakes may lead to fading, etc. - it's fine to "gear down" and use the effect of engine braking to slow the vehicle without over-taxing the brakes.


In situations like that it's better to keep speed down by braking fairly hard & then releasing the brakes than by keeping the brakes applied.

pgranzeau
05-10-2007, 02:32 PM
Now, in certain situations - such as a long downhill grade, where it's possible that prolonged use of the brakes may lead to fading, etc. - it's fine to "gear down" and use the effect of engine braking to slow the vehicle without over-taxing the brakes.

In situations like that it's better to keep speed down by braking fairly hard & then releasing the brakes than by keeping the brakes applied.

You know, D2 gears and the like are mandated by law to provide engine braking in situations where normal friction braking might get overused. Boil the brake fluid, and you no longer have brakes (other than the parking brake). Even my Prius, which doesn't really have any gears at all, has a means of engaging engine braking.

ChevyMan
05-11-2007, 06:17 AM
I've gotten some cons and some pros on this issue of using the lower gear so I'm still somewhat uncertain as to whether I should continue doing the way I'm doing it or not. If you must know, the roadway is only less than quarter mile distance from the top of the grade to the signalized intersecton and I do tap on the brakes occasionally to aid the engine's braking. Am I making any sense? I've been doing this for a very long time and so far nothing negative have happened. You are always advised to use the lowest gear depending on the steepness of the incline to save on brake lining wear.

I'm hoping to hear others' opinion on this matter.


Well, as I wrote earlier, the primary purpose of your brake system is to slow the car down. It's ok to use the brakes for the work they were designed to do. Now, in certain situations - such as a long downhill grade, where it's possible that prolonged use of the brakes may lead to fading, etc. - it's fine to "gear down" and use the effect of engine braking to slow the vehicle without over-taxing the brakes.

But the situation you've described is not that extreme; just a short downhill stretch. I doubt you're doing any damage - but why "save" the (cheap, easy to replace) brake shoes/pads at the expense of your transmission? You're making it work harder, unnecessarily, etc.







Still........

DonTom
05-11-2007, 08:55 AM
"You know, D2 gears and the like are mandated by law to provide engine braking in situations where normal friction braking might get overused. Boil the brake fluid, and you no longer have brakes (other than the parking brake). Even my Prius, which doesn't really have any gears at all, has a means of engaging engine braking."

You made a very good point! It's better to boil tranny fluid than brake fluid!

A broken tranny or blown engine (I have had two piston rods fail while going down hill) is a lot better than having an accident from not having any brakes. Most automatics do have a second gear. If they don't expect us to ever use it, why is it there?

However, perhaps it's almost as good to do the opposite, use the brakes until they start to feel strange and then use the tranny until the brakes cool off a bit.

BTW, how does your engine braking work in the Prius?

-Don-

Eric
05-11-2007, 10:14 AM
Now, in certain situations - such as a long downhill grade, where it's possible that prolonged use of the brakes may lead to fading, etc. - it's fine to "gear down" and use the effect of engine braking to slow the vehicle without over-taxing the brakes.

In situations like that it's better to keep speed down by braking fairly hard & then releasing the brakes than by keeping the brakes applied.

You know, D2 gears and the like are mandated by law to provide engine braking in situations where normal friction braking might get overused. Boil the brake fluid, and you no longer have brakes (other than the parking brake). Even my Prius, which doesn't really have any gears at all, has a means of engaging engine braking.


Sure.. that's true.. but as I wrote previously, Chevy's situation doesn't appear to be such a situation. Hence my recommendation to just use the brakes normally - and let them do the work they were designed to do!

Eric
05-11-2007, 10:19 AM
Right - but we're talking about fairly extreme conditions in that case - not what Chevy's related. He's not descending Pike's Peak or some mountain pass in Montana, etc.

I agree in those situations, engine braking is often necessary - and safer than counting on the brakes alone. But for ordinary driving, the brakes should not need "help" from the transmission to do their job properly.

PS - In a hybrid like the Prius, "regenerative braking" uses the inertia of the vehicle to drive a generator, to transform the nergy of forward motion into electricity - which is used to help keep the battery charged.

ChevyMan
05-11-2007, 05:19 PM
Of course if there was no signalized intersection at the bottom, I would descend in Drive and apply my brakes intermittently to control the speed as one normally does, but in my case, I'll never know if the lights will change so I use L2 merely as a precaution.
FWIW, I drive this section of the highway maybe only once a month or so, not daily.

DonTom
05-12-2007, 02:15 AM
"PS - In a hybrid like the Prius, "regenerative braking" uses the inertia of the vehicle to drive a generator, to transform the nergy of forward motion into electricity - which is used to help keep the battery charged."

That must be quite a large generator if it slows down the car as much as a second gear. But IAC, that sure is a good idea to let a type of downhill "braking" do something useful.

-Don-

Eric
05-12-2007, 07:28 AM
"PS - In a hybrid like the Prius, "regenerative braking" uses the inertia of the vehicle to drive a generator, to transform the nergy of forward motion into electricity - which is used to help keep the battery charged."

That must be quite a large generator if it slows down the car as much as a second gear. But IAC, that sure is a good idea to let a type of downhill "braking" do something useful.

-Don-


The "engine braking" effect is considerable - but most hybrids are set up so that it must be engaged (by moving the gearshift selector to the appropriate detent). When you're in "drive" the effect is much less noticeable...

DonTom
05-12-2007, 08:30 AM
"When you're in "drive" the effect is much less noticeable..."

Perhaps to get better MPG. It's probably charging at a much higher current when going down hill with the gearshift moved for downhill.

-Don-

mrblanche
05-12-2007, 11:03 AM
Some cars have very little engine braking. Hondas are noted for this, and there is even a warning to Honda drivers on Mount Washington in New Hampshire. Many of them arrive at the bottom with their brakes smoking.

pgranzeau
05-12-2007, 02:00 PM
BTW, how does your engine braking work in the Prius?

I live in the flatlands. I have never had to actually use it. Remember, the car also uses regenerative braking, where the traction motor becomes a generator and recharges the traction battery. If the traction battery reaches a "fully charged" state, then the car wil use the IC engine for braking, as well, and you can hear the engine suddenly become very busy, indeed (until then, it has been turned off completely, and hasn't been turning). People I have seen discuss it in the Prius-2G Group say it works very well. Remember, the Prius doesn't really have a transmission, just a balancer between the IC engine and the traction motor which has the effect of a variable speed transmission.

DonTom
05-12-2007, 04:35 PM
"Remember, the Prius doesn't really have a transmission,"

Electric engines don't have much need for such. Electric motors have a lot of torque until they burn out from overload. BTW, what is the total battery voltage in those things? How many batteries and where are they located? I never even looked inside a hybrid, however they are fairly common here in the SF Bay Area because during commute hours, they can use the car pool lanes with only one person and no toll at the bridges. Same for motorcycles.

-Don-

pgranzeau
05-13-2007, 12:21 PM
Electric engines don't have much need for such. Electric motors have a lot of torque until they burn out from overload. BTW, what is the total battery voltage in those things? How many batteries and where are they located? I never even looked inside a hybrid, however they are fairly common here in the SF Bay Area because during commute hours, they can use the car pool lanes with only one person and no toll at the bridges. Same for motorcycles.

The current Prius uses a 276 V electric motor with 44 hp, 258 lb-ft of torque, and a 1.5 liter 76 hp Atkinson cycle engine, together they give decent performance. The traction battery is located behind the rear seat, low in the car, just ahead of the gas tank, I believe. There's a very small 12V battery to operate the electronics while the car isn't in use. I've never had the hood up (but modern engine compartments are so jammed full of stuff one can't tell what is what, anyway). I believe that I, too, have the right to use HOV lanes (although I seldom go on an expressway, regardless), in Virginia.