Recently I have been shifting down with my automatic transmission to slow down at lights or coming off an exit on the highway. Is this OK to do during regular driving on a regular basis?

 

No...use your brakes to slow down. It's cheaper to replace the pads and rotors than the transmission.

 

... and we can change the brakes in our driveways -- I sure can't change a transmission in my driveway!!! You know, I don't think I could change a transmission even if I had access to a lift!!

Regards,
Paul...

 

As the others said…definitely use your brakes instead of your tranny. The only time I would consider downshift is when you’re descending down a steep slope.

 

OK, I'll be the Designated Dissident today. Has M-B stated officially that "manual" tap-shifting of the transmission causes wear beyond normal automatic operation? The manual, in describing tap-shifting, doesn't say anything about limiting its use to avoid wear. The only things it warns against are the usual dumb moves like coasting in neutral. The transmission's logic will override any "manual" downshift requests that would overspeed the engine.

I still miss my manual-transmission BMW 528 and sometimes I'll tap-downshift the E500 going into a corner, so that I can apply power through the corner instead of coasting. I can't speak about the 7-speed, but the 5-speed generally doesn't downshift far enough or fast enough on its own when I slow for a corner. It's no substitute for a clutch, but manual downshifting often seems to keep the engine in a better part of its torque and power curve. But then, that's not really substituting the transmission for the brakes, so maybe it's OK.

 

What wears down the transmissions is constant shifting UP or DOWN. Like it was also stated above, if you are descending on a constant steep slope, you can safely downshift because the transmission is NOT shifting. On prolonged downhills, the transmission is in one gear and then the Engine does the stopping. This is fine to do.

The problem with downshifting to stop at every light and coming down off-ramps is that you are having to downshift a few gears and this downshifting is putting a little extra wear on the transmission's bands.

I think that it is a good idea to practice and know how your car downshifts. You never know when you might have some sort of failure. However, brakes were designed to do the braking in normal driving situations.

I personally only downshift in city driving when I might have passed someone aggressively and then I don't want them to see that I had to immediately put on the brakes ahead of them. So I downshift and keep my brake lights off. I only do this about twice a year and when I am feeling stupid, so I don't really worry about wear on the transmission. Otherwise, I keep the car in a low gear when driving up and down the mountains here in Colorado. But like I mentioned, I don't always make the transmission downshift and raise the RPMs of the engine in a hurry while slipping the clutch bands.

Something that should also be noted is that the wear from downshifting is not any greater than the wear from up-shifting. This is if you have the same RPM differential between shifts. So the transmissions can take it, but why make it work twice as hard?

Steve

 

i do it at least once a day, after 25k havent had any issues but who knows what it can do in the long run... only time will tell but ive started using the brakes again, (after 25k also no issues lol)

 

This is exactly what the shifter is there for. I sometimes I do the exact same thing! Sometimes, when I am making a loop on an on-ramp to get on to the interstate I also put it in a lower gear so that the engine is revved and ready to deliver power when I get on to the acceleration lane. I belie that this actually reduces transmission wear because the transmission does not have to do a violent downshift when you need the power. Instead the gear and the rpms are perfect for acceleration. I also think that this saves wear on motor mounts since it does not jolt the car with a 2 or 3 gear downshift at once.

Like you mentioned though, this does not constitute power braking and does not wear the transmission down (if at all). Like I said, I consider this to be the intended purpose and use of the touch shift.

Steve

 

This is probably a bad habit to get into. On a slick intersection or ramp you could end up looking east in the west bound lane. But then again, we have 6 months of winter in my neck of the woods.

 

Remember though, the original poster suggested that he was using the downshifting to actually brake the car. This certainly does put stress on the transmission, and may shorten its lifespan. Certainly the risk to the transmission outweighs the longer life you will get out of your brake pads and rotors.

 

Actually, engine braking is more controllable on a slick surface (snow, rain) than regular breaking (not including the help our MBs get from ESP).

 

Actuall, your are wrong. Pop it in a lower gear from drive on a icy surface without using the brakes. You'll see what I mean.

 

I usually totally avoid downshifting (even on downhill slopes) when it is snowy or icy outside. I think that the SBC and ABS system works much better than the ESP.

THIS IS WHY:

If you only have a RWD E and you downshift enough to cause wheel spin (right when the downshift happens), then that wheel has already lost traction, so the ESP will not gain anything by putting on the brake on that wheel (which might be what is needed to rectify the car's trajectory. The car will be fighting itself, but you at least have the two front wheels disconnected from the tranny.

If you have a 4-Matic, then you can really screw things up by downshifting too much in snow or ice. This is gone over in winter driving school and there is no arguing this point.

The SBC system and ABS performsdexsZ best when it is the only system slowing the car down. The only issue is that when I drive down steep downhills in bad weather I simply have to slow the car way down and keep it at about 25 MPH in 2nd gear and then I put on the brakes sparingly to slow down. Making the car downshift is a recipe for disaster on snow, ice and low traction satiations. On a RWD E, downshifting is no different than using the emergency brake to stop, the rear wheels have the least braking power and if there is too much braking torque on them they just lock and skid.

If you don't believe me, come out here and drive in a blizzard, you will see what I mean.

Steve

 

Yes, this is correct. However, I should point out that when I downshift on the ON ramp I am NOT slowing the car down. I am still on the gas pedal so the RPMs will rev up immediately and maintain the speed that I am traveling.

I know that you are referring to braking here, but I just want to make sure that it is clear that I do this for better acceleration response and less jolting of the car.

I think that we are on the same page here though.

Steve

 

Right, my comment was directed to the originator of this thread as I was relating to slowing the car on a slick road by shifting into a lower gear rather than using the brakes.

Being from Colorado, I sure you know what I was alluding to, having the car do a 180 on a slick surface by down shifting rather than moderate braking.

 

Ok, I have read all of the comments and have a question about all of the logic. If you are driving on cruise control and go down a hill, the computer first reduces the gas and then if the car still increases speed, the transmission is downshifted. There seems to be a rev-matching algorithm that is used and there is no apparant jerk. Does the computer rev-match when manual downshifted? If so, there should be minimal wear on the transmission.

 

Actually I usually don't shift in poor conditions but good conditions (80 mph off of the ramp). In bad weather I would never attempt this...

 

So true!

I used to down shift to save brakes, and brake dust! but this was in my prior Volvo V70 and VW Passat, but I haven't since done it on the MB, reason being it's not good for the car. It's good to down shift on long downhills, or to aid in stopping in a rapid stop situation where you don't want to slam the brakes on, but for normal daily driving it would wear on the torque converter and transmission bands. I am also (FYI) putting my transmission on a 13000,39000,65000,91000 fluid change interval... i.e. a change at 13K (in a month or so), and then every 26K.. This life time fluid fill is


If on the other hand, you lease the car, and turn it in before warranty expires.. do what ever you want, including down shifting at every stop! And save the brakes which you have to pay for! It's car abuse, and I can't myself do it, but I'm sure someone here has no problem with it.

 

Well, hit the brakes on an icy surface, and you'll get the same thing. Trying to slow your momentum on a slick surface can always lead to sliding. But keeping the wheels moving gives you the most control on a slippery surface. This is also the design behind anti-lock brakes.

Now of course, this is assuming that the driver knows how to effectively downshift. Going at 60 mph for instance and then downshifting to a much lower gear could cause you to slide more than slight braking.

 

Actually, this is not entirely correct. If your wheel loses traction, whether it's from braking, downshifting, or whatever, ESP can brake the individual wheels to the point where the slipping wheel regains traction. It's not all about the one individual wheel. If your right rear wheel loses traction, ESP can brake the other wheels to help regain traction.

Actually, I'm interested in how this could "screw things up" as you say. Also, what winter driving school is saying this? All wheel drive is designed to help you get traction by directing the power to any wheel. When braking, this provides no extra help at all unless the engine is helping to slow the car down. Of course, if the transmission is not downshifting, then this would not be the case.

Again this is not true. These systems are designed to work together. In most modern cars with an automatic transmission, the car does downshift as you slow down, although it's the brakes that are doing most of the work.

Again, this is not accurate. But I do agree using the brakes in addition to a lower gear is an effective way of slowing down (or maintaining a slower speed) while maintaining control. However, there is a HUGE difference between downshifting and using the E brake. The E brake will lock up the rear wheels. No ABS, no SBC, no ESP, just locked up rear wheels. Your rear wheels will lose traction in almost every instance when you do this. Keeping your rear wheels turning helps you maintain control.

I've had my share of driving in snow, and am willing to bet that I have probably logged more hours of "snow driving" than most people on this board.

 

Not to mention the engine.

Just as the more miles on a tire, the closer it is to being worn out, the more revs on an engine ... .

Mercedes brakes are probably good enough, but in mountain driving I do prefer using lower trans gear downhill. Don't expect continual braking will lead to fade, but with engine braking assist there's even more margin, and it just feels better to control car with throttle rather than brake. On level roads, freeway offramps, etc., it's mostly silly.

 

My manual trans BMW 533i did a 180 just from letting off throttle. Fuel injection shuts off in that situation. Must declutch, too. Auto trans much better in slick conditions.

 

“”Actually, this is not entirely correct. If your wheel loses traction, whether it's from braking, downshifting, or whatever, ESP can brake the individual wheels to the point where the slipping wheel regains traction. It's not all about the one individual wheel. If your right rear wheel loses traction, ESP can brake the other wheels to help regain traction.””

The ESP does not work that quickly on loose surfaces like slippery snow and ICE. When you are slowing down with just two wheels and they are the rear wheels, it is very possible that you will fishtail AT LEAST one foot before the ESP even ties to compensate. I have tried it and this is what my car does (even with Blizzaks). Once the ESP turns on, it is not that quick to correct (since you are on ice) and usually causes the wheels that is being used to compensate the slide to skid too. What you end up with in this situations is sort of a controlled skid. If you just use the brakes, the ABS prevents fishtailing so the ESP hardly ever has to turn on in the first place. The ESP is all about the individual wheels, look at the video demonstration on the MBUSA site and you will see that only one wheels is being stopped at a time.

My issue here is that once you are in a skid you are relying on the ESP to stop you skid. If you were using regular brakes, the ABS starts to work first and can modulate stopping at each wheel and ensure a straight stop (which downshifting CAN NOT)


“”Actually, I'm interested in how this could "screw things up" as you say. Also, what winter driving school is saying this? All wheel drive is designed to help you get traction by directing the power to any wheel. When braking, this provides no extra help at all unless the engine is helping to slow the car down. Of course, if the transmission is not downshifting, then this would not be the case.””

I guess that your experience in snow driving does not include old stick-shift 4X4 trucks or SUV’s (for that matter my old 1986 Audi Quattro). Here is your quote: “All wheel drive is designed to help you get traction by directing the power to any wheel. When braking, this provides no extra help at all unless the engine is helping to slow the car down.”

So to sort of confirm what you stated here. If you decide to downshift on a AWD car and the engine is slowing down the car, all 4 wheels are doing the stopping. This means that if your downshift was relatively aggressive all 4 wheels can loose grip on slippery surfaces. Now what? The ESP does not turn on if the car is skidding in a straight line. The ABS will not turn on if you are not hitting the foot brake at the same time as you are downshifting. And most importantly, Even if you were hitting the brakes, the ABS would only let go of the brakes, but the engine would still want to stop the wheel and keep it locked. This is all if you are skidding in a straight line.

So now iF you are skidding sideways, you are relying on only the gyro sensor in the car for the ESP because the speed sensors on each wheel are all fooled. Also, even if the ESP was not confused by erratic wheel speed at all wheels how would any ESP action help if you have no traction on any wheel because of the downshifting power making it loose traction?

On a AWD vehicle you stand to loose grip on all 4 wheels and break all 4 wheels loose. On a RWD vehicle you theoretically have a chance that the front wheels might still have some grip and could conceivable help in stabilization. Again, this is during strong deceleration.

The winter driving school I am referring to is the one that was operating out of Steamboat Springs. They used to have Audi Quattros tricked out at FWD, RWD, AWD and 4x4. This experience was priceless. It really gave you a perspective on the pluses and minuses of each.

“”Again this is not true. These systems are designed to work together. In most modern cars with an automatic transmission, the car does downshift as you slow down, although it's the brakes that are doing most of the work.””

Yes, this systems are designed to work together. But they all rely on the laws of physics and on grip. The minute you have no traction, none of the systems will work (together or not). No grip caused by a sudden deceleration will render the other systems such as ABS and ESP and 4ETS (on 4-Matics) totally useless as long as the grip is lost.

“”Again, this is not accurate. But I do agree using the brakes in addition to a lower gear is an effective way of slowing down (or maintaining a slower speed) while maintaining control. However, there is a HUGE difference between downshifting and using the E brake. The E brake will lock up the rear wheels. No ABS, no SBC, no ESP, just locked up rear wheels. Your rear wheels will lose traction in almost every instance when you do this. Keeping your rear wheels turning helps you maintain control.””

If you are in a RWD car and you downshift, you can and will lock up the rear wheels. Now, by locking up the wheels I mean that they will not spin at the speed they need to. I can easily use the parking brake while driving on ice/snow and make the rear wheels loose traction while they are still spinning a little bit. This is very similar to downshifting (if you downshift a few gears on slick surfaces.

Now this is how downshifting on a RWD car can be even worse than the parking brake: If you do apply the parking brake to the point of 100% lockup at the rear wheels, you at least have both rear wheels locked and causing the same amount of drag. If you are driving straight, you MAY still skid in a straight line. If you downshift and you slightly loose traction or completely loose traction, the differential might cause one wheels to loose catch up more than the other and guarantee that you will fishtail. My 300E was incredibly adept to fishtailing. Remember, ABS and Trac control is useless in this case, only the ESP and the grip on your front wheels can possibly correct this.

“”I've had my share of driving in snow, and am willing to bet that I have probably logged more hours of "snow driving" than most people on this board.””

I don’t doubt this. Nothing that you are saying is wrong because I see how you interpreted my statements. It is obvious that you know what you are talking about, but I would be writing a novel if I had to totally explain what I am trying to say. I drive in a lot of different conditions that in the past have made my cars do very strange things. I learned to experiment with my cars when I have an empty parking lot with a lot of snow and nothing to hit. I have personally tried pulling the parking brake, downshifting and putting the car on Dynamometer testing mode to see how the car acts w/o ESP, ABS and 4-ETS. The last thing that I want to do is be surprised when the in an actual traffic situation, so I test these things out and try to react in the safest way to emergencies along with avoiding stupid moves like significant engine braking on low traction situations.

Steve

 

This is exactly what I am also talking about. My 300E was like this too.

Steve

 

Ok, next time it snows try this: turn ESP off and from a stop, try and take a corner. You will see that you fishtail. Now turn ESP on, and try the same thing. You will see that as soon as the car starts to slide, ESP takes over and stops it.

You are correct in once sense. There is no system that can reverse the laws of physics. But to imply that ESP will never help you in a situation where you are sliding is inaccurate. And ABS does not prevent fishtailing. It helps to prevent it, but again, the laws of physics will take over no matter what.

If you were sliding to the point where the power to the tires could no longer prevent you from sliding, then ABS will also not prevent you from sliding.


First, yes, I have plenty of experience with manual transmission cars and trucks, and started driving long before anti lock brakes came out. I also have experience driving large trucks including tractor trailers.

An AWD car DOES NOT provide power to all 4 wheels at the same time, so a downshift in such a car would not effect all 4 tires.

There is no method out there that will completely guarantee you a no-slide situation every time. Of course aggressive downshifting is bad. So is aggressive braking, even on a car equipped with ASB. And yes, ESP WILL help you in a situation where you are sliding straight. It will still sense the wheel that is sliding along with the wheels that are not and apply braking.

You are mistaking AWD with 4WD. Most AWD vehicles only provide power to one or two wheels at a time. They just have the ability to supply power to all 4 wheels, just not at the same time.

This I agree with. But please don't mistake proper downshifting with "sudden deceleration". Downshifting to slow down is not necessarily a sudden deceleration.

Well, to me, "locking up" implies that they are no longer turning. When your engine slows down the forward momentum of your drive wheels, they are still turning. If this is done properly, it can slow you down while maintaining control of the car. Similarly, when you brake, if you brake hard, you can and will slide. When you better control your braking, you better control the car.


There are two ways of getting out of a slide when your car is fishtailing. One is to steer in the direction of the skid which catches the front up to the rear. In driving school, they also tell you to lift your foot completely off of the brake. This allows power back to the rear wheels giving them an opportunity to "bite" and help straighten you out. The other way is the ability to individually brake certain tires. When the rear swings out to the right on a skid, braking can be applied to the right front tire which will encourage the front end of the car to catch up to the rear. Much like steering into the skid. This is what ESP does. By the way, ESP is traction control.


Steve, although I do disagree with some of your points, I too understand what you are saying. I think the whole thing began really with a misinterpretation of downshifting. This term can be used for different things. Downshifting to pass for instance is completely different than downshifting to slow down. However, slowing the car down by controlled downshifting in addition to braking is an effective way to maintain control of a car. With ABS, and traction control technology today, there may be easier ways of controlling the car. But if anyone's ever spent some time in the snow in an older car without anti-lock brakes, or traction control, etc., they most likely learned control via downshifting.