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ASKED BY:

Douglas J Dayton

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Yes

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Transmission

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Question

I have been fortunate to have driven BMW cars and motorcycles for 49 years. Until my last two vehicles all of my transmissions have been standards. My first wife shared the appreciation of a gearshift and clutch but my second wife was apparently never able to get the feel and timing (much to the frustration of her first husband). So, when I updated from my Z3 Coupe to a Z4 Coupe/Convertible and added an SAV to my collection, I was forced to consider automatics for the first time. I still shift (E89 – six speed, F25 – eight speed) and in Sport Mode the transmissions do pretty well. Assuming that I maintain proper shift points, am I shortening the lives of these transmissions compared to letting them decide on their own? Is Sport Mode harder in any way on the engines or transmissions than Normal Mode?

Answer

Hello Mr Dayton, the answer to your question is both yes and no. First, let’s tackle the yes. I would not be able to answer this question with any certainty without a VIN number, however, a large number of transmissions in European vehicles are not actually automatic. In BMW speak they are DSG transmission, electronically shifted manual transmission, therefore no clutch pedal. This may be the case for your vehicles. In both cases, automatic or manual transmissions, shifting at a higher RPM will add more mechanical stress to it, that will cause to shorten it’s life. What I cannot tell you is by how much time. This will depend on the way the vehicle is driven among other factors. This scenario is especially true in Florida. One of the biggest enemies of transmission is fluid temperature, our ambient temperature is already high and shifting at a higher RPM will cause more heat to be introduced to the transmission. As long as you are not going too far with the RPM you should be fine.

he other factor that will help extend the life of any transmission is service. Per BMW and most manufacturers, the transmission fluid is lifetime and does not have to be changed. The issue here is the word lifetime, most people assume that lifetime refers to the lifespan of the part and that is not true. Here is the difference, every part on a vehicle has an expected lifetime, which means how long is the usable life of that part, lifespan is how long that part actually lasts. Taking transmission as an example, the lifetime is usually 100000 miles, now, most transmissions will actually last a lot longer, but that means that the transmission and therefore the fluid will only last 100000 miles. I usually recommend replacing the transmission fluid and filter at 60000 miles, you can also reference Mike Miller’s Old School Maintenance Schedule as it is a great document. Here is a link to it: https://www.dslreports.com/r0/download/2294029~a7ccced57c514756e4c445baa2542b06/Lifetime%20Maintenance%20Schedule%20v03.13.pdf

As for the no, your vehicle’s many computers will do their best to keep you from doing harm to any of the parts, engine, transmission, etc… This is the reason for the “limp home mode”, which happens because one or more of the computers have determined that there is an issue, whether created by the driver or a mechanical fault that will likely cause a failure. It will respond by limiting the power, shifting, vehicle speeds, etc… in order to allow you to pull over without causing damage.

The other safeguard is the “drive-by-wire” nature of most vehicles on the road today.  I’ll illustrate this by using the example of a throttle body. Earlier throttle bodies were cable-driven, therefore the amount of movement applied to the gas pedal will be directly correlated to the amount of movement on the cable. This is referred to as a command, it does not matter if the amount of throttle will cause engine damage, the cable will follow what your foot does. With modern drive-by-wire throttle bodies, your input on the gas pedal is a request. Let’s say you are driving at 45MPH, you then decide to apply a large amount of throttle angle that will likely cause the wheels to lose traction, in this case, the traction control computer will intervene and not allow that input to happen. When you request any amount of throttle the computers in the vehicle will analyze the request and if they deem it appropriate it will allow it, if not then it will not.

In short, while there is a possibility of your driving causing an issue there is not a likelihood. Please let me know if you have any other questions. Thank you.

Gil Neves

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