[Technical question] Why would damage occur when being towed?

[JCL]

Originally Posted by autoque

Ah~, so it wouldn't be advisable to go down hill in neutral even with the ignition on. I liked doing that 'cause I thought it saves some fuel while doing so. Never did I think it could damage the transmission and transfer case.
I'll use neutral only when going through the car wash tunnel from now on.

I'll skip the car wash comments, since I use them too (touchless though)

Coasting in neutral down a hill won't save you any significant amount of fuel, since the fuel injection cuts fuel flow on over-run. You are also adding wear to your transmission, as noted above. It won't affect your transfer case, since the transfer case doesn't know the difference.

More importantly, it is unsafe. You have three types of control of your vehicle; steering, braking, and acceleration. Putting the vehicle in neutral while moving takes away the last one of those, acceleration, if you have an impending accident. That is the reason it is also illegal in most jurisdictions (not sure about your state).

[autoque]

Speaking of Neutral gear, I also like to put in neutral and use parking brake during long stops at traffic lights. This wouldn't put extra wear and tear to anything would it? Just wanted to make sure since the topic came up. Thanks.

[Thunder22]

Originally Posted by autoque

Speaking of Neutral gear, I also like to put in neutral and use parking brake during long stops at traffic lights. This wouldn't put extra wear and tear to anything would it? Just wanted to make sure since the topic came up. Thanks.

Why?

[autoque]

Originally Posted by Thunder22

Why?

I'm not particularly thrilled about being in Drive gear when I'm at full stop for a long traffic light. Just something about the car trying to go forward and me braking it (or Autohold doing the braking for me) doesn't feel so good, like the vehicle is more stressed. When put in Neutral, there's less vibration and noise in the vehicle than when in Drive. So it just feels better.

[Penguin]

Originally Posted by autoque

Speaking of Neutral gear, I also like to put in neutral and use parking brake during long stops at traffic lights.

The "Autohold" function would do the brake for you automatically, but I don't think it puts it into neutral.

[FunfDreisig]

Originally Posted by Penguin

The "Autohold" function would do the brake for you automatically, but I don't think it puts it into neutral.

I've been wondering about that 'turbo lag" when pulling away from a stop that many 35d owners have noted/described (including me). I'm beginning to wonder if the programing of the automatic transmission, that many have suggested is the main culprit, may be more than just trying to start off in 2nd. It may be that the automatic transmission is going into something like neutral when we come to a full stop, particularly when we engage AutoHold.

It would be interesting to find out how much load is removed (fuel saved) by manually shifting into neutral.

Funf Dreisig

Edit: I ran an experiment today where I released the brake on level ground. Our E70 35d barely inched forward. I don't have our E53 4.4i for comparison anymore. But my remembrance is that if I let my foot off the brake, it would trundle off at a brisk pace This may be a case where the weak torque of the 35d at idle actually works in the favor of just putting your foot on the brake (or using AutoHold) at stop lights.

[Weasel]

No, that is perfectly fine.

[Penguin]

Probably has little difference whether or not one shifts into neutral a traffic lights, but there are a couple of factors to consider:

(1) If one regularly does this, you are probably shifting the mechanism and valve/solenoid about 10-40 times more than the engineers anticipated, e.g., in 50k miles you will have "exercised" the mechanism about as much as the design engineers expected to happen in 500k - 2 million miles of use. Odds are the valve/mechanism is over-designed enough this doesn't make a difference, but I probably wouldn't do it.

(2) I seem to recall that in a motorcycle safety class I took that they recommended against being in neutral at stop lights for safety reasons -- if something happens where you wish to move quickly, you must shift into gear first.

Personal decision, but since the transmission is designed with the expectation that people will not shift into neutral, and since BMW auto transmissions are a known weak spot of BMWs, I leave it in drive.

[autoque]

^ That makes sense. I'm trying to grow out of that habit these days for that reason as well.

[Mujahid]

100%, thanks for that.