transmission questions..

Any time you shift gears (either up or down), you are causing some degree of wear on the entire driveline. If the shifts are done smoothly, the amount of wear would so miniscule that wouldn't even be worth worrying about.

The clutch is a slightly diffferent story. If a person frequently slowed down by downshifting, the clutch would not last as long as it could/should. Given that a set of brake pads costs many, many times less than a new clutch job, the choice to use only the brakes to slow down seems like the natural choice. I don't even want to ask what a rebuild transmission would cost for the 3 Series....

Re: Re: transmission questions..

ff said:

Any time you shift gears (either up or down), you are causing some degree of wear on the entire driveline. If the shifts are done smoothly, the amount of wear would so miniscule that wouldn't even be worth worrying about.

The clutch is a slightly diffferent story. If a person frequently slowed down by downshifting, the clutch would not last as long as it could/should. Given that a set of brake pads costs many, many times less than a new clutch job, the choice to use only the brakes to slow down seems like the natural choice. I don't even want to ask what a rebuild transmission would cost for the 3 Series....

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Great explanation ff :thumb:

So, then do you guys only downshift when you are stopped? My guess is that you don't. Do you ever simply take your foot off the gas to slow the car down (like when you see a cop ahead) using the engine and gearing (and tire friction)?

Do you ever drop to 4th (or maybe even 3rd) to pass on the expressway, or downshift into 2nd preparing to exit that high-speed corner, etc. It's all the same!

"Yeah, but we ALWAYS heal-toe and match the revs when we do this."

Exactly! The potential problems that can arise in the transmission or engine result from sudden changes (e.g., that jerk you feel when you accidently miss-match the revs when you downshift). If you match the revs to the lower gear and then shift, you can use that gear to continue to slow you down. That way you remain in gear so that should the need arise, I can get on the gas to avoid trouble (doing it this way ensures that you will also be in the proper gear for this as well).

This is the way I've always done it and I've never had to replace a clutch, transmission, or engine. I can't imagine BMW's clutch, transmission and engine is any different than my old toyota with 125,000 miles on the original parts. Now, can you do it with step? I have no idea. It would seem that the rev limits and such that are built into the system would make it less effective, but that's just a guess.:dunno:

BS' Bimmer said:

Do you ever drop to 4th (or maybe even 3rd) to pass on the expressway, or downshift into 2nd preparing to exit that high-speed corner, etc. It's all the same!

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Bascially, never. Especially with the meaty torque in the 330, as well as the fact that it's geared to cruise the highway at an RPM that's close to it's torque peak. A stab of the throttle in 5th gear will probably get you to 80 or 90 MPH quicker than if you downshifted and floored it. Haven't tried the later, so I can't say for sure. But I have tried the former (too many times to count) to know that the car really shines here. :thumb:

Here's what I posted over on the org to this question:

Regardless of wear issues, I feel more in control of the car when the engine speed has some relation to the vehicle speed as the car slows, unlike when just coasting.

I feel like I'm causing excessive break wear when I don't use engine braking as much as I could.

I feel like engines and trannys were made to sustain such "negative torque" (for lack of a better term) as part of normal operation, and not as something that would cause excessive wear.

And, most importantly, to me it just feels better.

Re: Re: transmission questions..

ayn said:

NEVER slow down your car by downshifting, brakes are much much cheaper than transmission and engine.

--Andrew

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Hmmm... I use engine brake a lot. Granted, I rev the engine up accordingly before downshifting. This way downshifts are smooth AND the engine speed is compatible with the ground speed...

Oh well, it's not like I keep cars forever...

Edit:

AYN, you've got Step, right? As you slow down using the brakes, don't you hear your auto tranny downshifting for you?

Plaz 330i said:

Here's what I posted over on the org to this question:

Regardless of wear issues, I feel more in control of the car when the engine speed has some relation to the vehicle speed as the car slows, unlike when just coasting.

I feel like I'm causing excessive break wear when I don't use engine braking as much as I could.

I feel like engines and trannys were made to sustain such "negative torque" (for lack of a better term) as part of normal operation, and not as something that would cause excessive wear.

And, most importantly, to me it just feels better.

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OMG I can't believe the amount of bad information being passed around here! This is the first post in the thread that's accurate as far as engine brake is concerned.

First of all, engine braking DOES NOT increase wear in transmission. Basically, the momentum of the engine is slowing down the vehicle. As long as the clutch (manual) or gears (auto) are engaged, the engine, drive shaft, and gears are all rotating at the same speed. No possible wear can occur. Also, when you downshift in an automatic transmission, the torque converter absorbs all the "shock" in the system, and on a manual transmission the ECU will automatically "speed up" the engine to catch up to the spinning gears, thus minimizing the wear in clutch when first engaged. Those who say that "downshifting will wear through the clutch" are wrong, you're only wearing through the clutch when the clutch disc is spinning against the flywheels...i.e. if you ride the clutch and let it engage over a long period of time.

Now, there are numerous advantages to engine braking in manual transmission cars. First, it leaves your car in the proper gear to come out of a turn or if the light should change midway or if the car in front of you pulls off. In driving school they always teach you to brake with BOTH FEET, one on the brake pedal and one on the clutch pedal so you can roll through the gears as your car slows down. Second, it reduces fuel consumption. The fuel injector and throttle closes off when the car is engine braking, since the wheels are turning the engine rather than the engine turning the wheel. There's a funny effect you'll feel when you're driving the manual...As you coast to a slower speed, you'll feel a "switch over" and a slight vibration when the momentum of the wheels can no longer sustain the momentum of the engine, and the fuel injection pumps gas into the cylindars to keep the engine turning when the ECU senses an impending stall. You get much better fuel economy when you engine brake rather than leaving the car in neutral and braking, because when the engine is in neutral the ECU is forced to inject fuel into the cylinders to keep the engine turning. It's a small difference.

As far as steptronic engines go, the only advantage would be that you'll be in the proper gear to come out of a turn or punch the gas when the slowpoke in front finally moves over.

I personally think, and practice engine brake as much as possible, and my Z3 when turned in for final inspection at the end of the lease showed little to no signs of wear...That clutch could have lasted a few hundred thousand miles on my driving habits.

I have the 2.5L engine so I have to "drive" the car to get the results I want. I engine brake to take a corner and I also double-clutch when I do the 5-4 or 4-3 shift. I do try to match revs as best as I can, but it takes practice. I believe these cars were built to be driven, but not abused. There is nothing more exhilerating then the 5-4 shift to pass. I haven't driven the 330 so I'm unaware of the power available at highway speeds, but I don't think a 5-4 shift would send you spinning out of control. If you match revs, you should be ok.

The HACK said:

OMG I can't believe the amount of bad information being passed around here! This is the first post in the thread that's accurate as far as engine brake is concerned.

First of all, engine braking DOES NOT increase wear in transmission. Basically, the momentum of the engine is slowing down the vehicle. As long as the clutch (manual) or gears (auto) are engaged, the engine, drive shaft, and gears are all rotating at the same speed. No possible wear can occur. Also, when you downshift in an automatic transmission, the torque converter absorbs all the "shock" in the system, and on a manual transmission the ECU will automatically "speed up" the engine to catch up to the spinning gears, thus minimizing the wear in clutch when first engaged. Those who say that "downshifting will wear through the clutch" are wrong, you're only wearing through the clutch when the clutch disc is spinning against the flywheels...i.e. if you ride the clutch and let it engage over a long period of time.

Now, there are numerous advantages to engine braking in manual transmission cars. First, it leaves your car in the proper gear to come out of a turn or if the light should change midway or if the car in front of you pulls off. In driving school they always teach you to brake with BOTH FEET, one on the brake pedal and one on the clutch pedal so you can roll through the gears as your car slows down. Second, it reduces fuel consumption. The fuel injector and throttle closes off when the car is engine braking, since the wheels are turning the engine rather than the engine turning the wheel. There's a funny effect you'll feel when you're driving the manual...As you coast to a slower speed, you'll feel a "switch over" and a slight vibration when the momentum of the wheels can no longer sustain the momentum of the engine, and the fuel injection pumps gas into the cylindars to keep the engine turning when the ECU senses an impending stall. You get much better fuel economy when you engine brake rather than leaving the car in neutral and braking, because when the engine is in neutral the ECU is forced to inject fuel into the cylinders to keep the engine turning. It's a small difference.

As far as steptronic engines go, the only advantage would be that you'll be in the proper gear to come out of a turn or punch the gas when the slowpoke in front finally moves over.

I personally think, and practice engine brake as much as possible, and my Z3 when turned in for final inspection at the end of the lease showed little to no signs of wear...That clutch could have lasted a few hundred thousand miles on my driving habits.

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Hack: I agree with almost everything you said. When I was learning how to drive a manual transmission in the mid-70's, I was taught to always downshift and utilize the benefits of engine braking. Based on my first hand experiences over the last 28 years, I do not believe that proper engine braking techniques places any additional wear on the engine or transmission.

In regards to automatics, engine braking is as effective as with a manual transmission. The manual selection of a lower gear as you are decelerating increases the vehicle's rate of deceleration, improves fuel economy by closing the fuel injectors, and also places the transmission in the proper gear for coming out of a turn, just like a manual.

I have always downshifted and utilized engine braking in all my vehicles, manuals and autos. I have never had an engine, transmission or clutch problem in any vehicle I've ever owned, including some that were driven well over 100,000 miles.

Yup... I agree. I also use engine brake a lot... And you guys are right about saving fuel. As you downshift, you can see the MPG gauge needle indicating 50+MPG right away...

Dan said:

Hack: I agree with almost everything you said. When I was learning how to drive a manual transmission in the mid-70's, I was taught to always downshift and utilize the benefits of engine braking. Based on my first hand experiences over the last 28 years, I do not believe that proper engine braking techniques places any additional wear on the engine or transmission.

In regards to automatics, engine braking is as effective as with a manual transmission. The manual selection of a lower gear as you are decelerating increases the vehicle's rate of deceleration, improves fuel economy by closing the fuel injectors, and also places the transmission in the proper gear for coming out of a turn, just like a manual.

I have always downshifted and utilized engine braking in all my vehicles, manuals and autos. I have never had an engine, transmission or clutch problem in any vehicle I've ever owned, including some that were driven well over 100,000 miles.

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ff said:

Bascially, never. Especially with the meaty torque in the 330, as well as the fact that it's geared to cruise the highway at an RPM that's close to it's torque peak. A stab of the throttle in 5th gear will probably get you to 80 or 90 MPH quicker than if you downshifted and floored it. Haven't tried the later, so I can't say for sure. But I have tried the former (too many times to count) to know that the car really shines here. :thumb:

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The point is that to accelerate quickly in 5th you need to punch it more than you would in 4th because torque is only part of the acceleration equation. The key to good accereration is to find that perfect mix of torque and horsepower. At highway speeds, you might be cruising along near the torque peak, however, you are well below the horsepower peak. Downshifting into 4th puts you closer to the HP peak (which is a significant improvement) while only losing a small amount on the downside of the torque curve (if there is any loss! I don't have the 330 torque/hp curve etched in my mind . . . sorry!). In other words, it puts you at a better mix of HP and torque which will imporve acceleration.

While you're right, punching the throttle in 5th will get you to 90MPH quickly (which is fine for everyday driving). . . but try going out and downshifting once. You'll get there slightly quicker, and have a lot more fun doing it!

I downshift with my step in manual all the time. I drive a lot of highway and do a 5-4 downshift whenever I get too close to the car in front and also when passing. We have some decent hills in Western SC and NC and standing on the brakes or waiting for the automatic to do the down shifting would make for some dull rides. I drive regularly from SC to Asheville NC with my Millenia (sorry to say) and even shift that baby's 4 speed slush box. After 172,000 miles I am still on my original factory brake pads. No problems with the engine either.
With my Bimmer I use each and every gear and go into first at times on tight turns.

Add me as well, supporting The HACK and Dan. They both gave very good explanations.

I have Step, and engine breaking works great. I have a post regarding this issue a while back. I am still learning the best way to use Step, and there is always something new I come up with. BMW's Step is the best auto tranny I have driven, but granted it is still an auto. However, rev-matching is almost possible.

ff said:

If shifting gears doesn't cause ANY wear, then transmissions should never need to be replaced, right? I mean, my transmission and the neighbor's auto transmission should last for over 10 million miles.

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I think the quote saying that shifting gears doesn't cause any wear is a little over simplified. However, if you downshift properly (heel toe and/or match the revs) any wear on the transmission and/or clutch is greatly diminished. I too have put well over 100k miles on several manual transmissions and have never had to replace a clutch. But that's not to say they wouldn't have to be replaced eventually.

I think the quote saying that shifting gears doesn't cause any wear is a little over simplified. However, if you downshift properly (heel toe and/or match the revs) any wear on the transmission and/or clutch is greatly diminished. I too have put well over 100k miles on several manual transmissions and have never had to replace a clutch. But that's not to say they wouldn't have to be replaced eventually.

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I totally agree. Its a machine...they will break eventually and meant to be replaced or repaired. There is nothing more satisying than the 5-4 or 4-3 double-clutch downshift at highway speeds.

jdlsc said:

I think the quote saying that shifting gears doesn't cause any wear is a little over simplified. However, if you downshift properly (heel toe and/or match the revs) any wear on the transmission and/or clutch is greatly diminished. I too have put well over 100k miles on several manual transmissions and have never had to replace a clutch. But that's not to say they wouldn't have to be replaced eventually.

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Exactly, and that's exactly what I said in my original post. But I was knocked down right away, and was told that shifting gears to aid in braking doesn't cause any wear.
Any action of metal-to-metal movement will cause wear, no matter how miniscule the amount is. There will always be wear.

Let's not even begin to discuss people that don't match revs perfectly to the trans. speed every single time.

I still contend that using the brakes makes a lot more sense, as they're easier and cheaper to replace than a clutch or transmission. Once you consider the extra time and concentration it takes to use shifting as a means to slow down, I'm sure you'd find that stopping distances are mostly shorter when you only use the brakes. Maybe a different argument could be made for auto trans. cars? Who knows (or cares?).

Oh, well... :dunno: