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

[Weasel]

No, that is perfectly fine.

[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?

[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.

[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]

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]

Originally Posted by Weasel

Note that I am talking about a non x-drive X5, no clutches in the transfer case to allow give, just planetary gears. With the X5 in neutral there is still a physical connection between the front wheels and the rear wheels.

Hi guys, this reply is a bit confusing - if the 2003 model can be towed with one axle lifted,(as per owners manual) and x-drive was released after 2004. It means that a 2003 X5 with planetary gears (pre x-drive) cannot be towed with an axle lifted or it will be damaged, as related in this post.
Does that mean that the owners manual is indeed incorrect.

Can some one please maybe answer these questions:
1) How does one tow a non x-drive X5
2) How does one tow and x-drive X5.

thanks, and great forum.

[JCL]

There is little discussion of towing with one axle lifted, as X5 owners tend to prefer flatbeds, because then there is no question of potential damage. You don't actually need a flatbed, however, and flatbeds can cause other damage if not deployed carefully.

These are in the reverse order to your questions, for reasons of clarity.

1) For an x-drive, from 2004 onwards, you need to ensure than axles are turning at the same speed (or both stopped) when the X5 is being towed. One way is to tow flat on the ground, with all wheels turning. Alternatively, if you don't have a flatdeck available, then you need to use wheel lift equipment on one axle, and put a dolly under the other axles (so that all axles are stopped).

2) For pre x-drive, up through 2003, the manual states that you can tow with one axle raised, for a limited distance and speed. Weasel's point is that the two axles are joined by gears. It isn't a fixed connection, but rather a planetary diff. As long as the transmission is in neutral, I can understand that it would work (but it would spin the input shaft). As an example, your left and right axles are joined by gears as well, and they can turn relative to each other. It isn't all locked together like a 4wd truck, with the two driveshafts geared together 1:1, as the front and rear axles need to be able to turn relative to each other to prevent binding in corners. The centre diff is used to create a torque split (32/68 on early X5s, IIRC). Again, when towing with one driveshaft fixed and one turning there is a distance and speed limitation, as you aren't lubricating the transmission. To be completely safe, treat it as an x-drive, above.

Weasel may be able to chime in and clarify the comment, as to the accuracy of the manual and my interpretation.

Edit: The following refers to the New Venture 125 transfer case that my 2003 X5 had. This was a Chrysler/GM joint venture company, now owned by Magna. The operating description is lifted from another board.

The NV125 is a full-time, permanent All Wheel Drive (AWD) transfer case with a fixed 32:68, Front : Rear torque split. TheNV125 transfer case has the following features-:
Permanent AWD.
Single Speed (i.e. No low range ratio).
Constant mesh centre differential with 38:62
torque split.
3/8" Pitch chain with 35 Tooth sprockets.
Splash lubrication via chain rotation.
Weight 23 kg.
The transfer case has no external controls and requires no input from the driver to operate. The unit contains a centre differential that allows permanent connection of the front and rear wheels to the driveline to achieve constant all wheel drive. The major components of the transfer case are-: the front case half; the rear case half; the planetary gearset; the main shaft; the input and output shafts;and the chain.

The front and rear cases are manufactured from cast aluminium. Both cases are bolted together and provide the bearing locations for the main shaft, drive sprocket, planetary gearset and front and rear output shafts. The front case assembly also houses the mounting bush, which is connected to the transmission cross-member when installed in the vehicle.

The transfer case receives torque from the transmission output shaft. The transmission output shaft is connected to the transfer case input shaft via a 38-tooth spline. Torque (62%) to the rear output is transmitted via the input shaft to the carrier (which carries the planet gears) then to the annulus (or ring gear), which is connected to the rear output shaft. Torque (38%) to the front output is transmitted via the input shaft to the carrier, then to the sun gear. The sun gear carries a 35-tooth drive sprocket, which drives the chain. The chain then drives another 35-tooth sprocket integral with the front output shaft. Because both sprockets have the same number of teeth, the rotational speed of the input shaft and front output shaft are the same.
The fixed torque ratio is arrived at by the leverage ratio of the annulus (ring) gear of the differential over the sun gear.



Item Description
1 Rear Output - 62% Torque
2 Sun Gear
3 Chain Drive to Front Output
4 Front Output - 38% Torque
5 Input - 100% Torque
6 Annulus or Ring Gear

[Mujahid]

100%, thanks for that.