I went through all of the transmission slam issues on my old E53 X5 4.8is with BMW, and as they share a fair number of components maybe the same reasons apply....

After a fair bit of research I found out the cause according to the technical people (I went up as high as the BMW board with my defects), but that is all history now.

The following is as it was explained to me, and although I don't like it, it makes sense....

So, it appears that in order to achieve the economy and emissions regulations in its' largest market (USA), BMW deliberately set the learning mode of the transmission software to run in an economy mode. It learns and learns until it has a VERY conservative mapping?? Anyway that's why the reset works for a while until it starts learning again.

The cars start off in 2nd at all times due to the fact that in stop start traffic, 1st would be both uncomfortable and poor on economy. The problem exists however that should you need to start off quickly then 2nd is unsuitable. BMW overcome that by measuring the speed at which you depress the gas pedal. If you are starting quickly, you will find that you tend to press the gas more urgently and the car leaps as it has sensed this.

If you start off slowly however and then increase the speed of pedal depression, the software takes a moment to identify, measure car pitch and a dozen other things it takes into account, change down to 1st and away you go..... the problem being however, that in the meantime you have continued to increase the revs of the engine and it is now dropping in to gear with higher revs... the auto equivalent of 'dropping the clutch'

IIRC, there are four separate programming modes being (these are my abbreviations) extreme economy (EE) Normal Economy (NE) normal sport (NS) and extreme sport (ES). Once the computer has sensed a change in the speed of pedal depression more than once in accordance with braking pressure, cornering force or whatever they are measuring, it changes into the extreme sport map and you find that the car revs and the transmission points seem very perky for a short time. This is why it transforms without you having to use the sport mode, and you will notice it holds a gear instead of changing in to a lower gear for economy.

It is all down to how fast and consistently you depress the gas pedal. Again, I don't like it but we are a small market for BMW here in Oz and we get to have what the rest of the world wants (or their regulations are).

The same thing happens on slowing down, although because it is measuring pitch, yaw, brake pedal pressure, throttle position, speed etc you can get a different result every time even though you think you are doing the same thing.

It also appears particularly common on the high torque (or power I can't remember) models, which is why some diesels, 550's etc have the problem more than others.

It is also why I canceled my M5/550 choice (as the 550 had the same detonation issues as my 4.8is) and went for a smaller 540. That has given me no issues and is to date the very best handling and performing car I have ever driven (love it!!)

Hope I have helped

Cheers


J

 

Agreed... I had the tranny slam and the dealer offered to do a CIP upgrade (31.2) and that has done the trick for me at this point. So far, so good...

 

1. Go to their sales dept, and drive a vehicle like yours. Then report to service.

or

2. Go to used car mgr. Ask him how much he will give for car that shifts like this. Then ask him how much if you fixed shifting. Then report to Service mgr.

Known as getting them over the barrel.

 

Its going in to a different dealer now, and i'm going to demonstrate this myself to their tech.

Seems a bit of a joke that some people accept this as a method of functioning. Maybe those individuals have a lot of money to waste and do not care how their purchases behave. I on the other hand expect my purchases to be right or they go back. I will keep you guys posted on what happens.

 

Any progress on this mate?