"The Lurch" does any of the tranny updates fix it?

[MADT]

So many mixed responses around this. I'm a little nervous about having the update, but if it make it better I dont want to miss out!

[MADT]

I new tranny would indicate you also would have upgraded software as well.

[MADT]

Yes that's what I want to get the tranny adaptions reset. Just in case

[rayxi]

Did a bit of digging and found this explanation of the issue. The poster owns a 535d which has the same GA6HP26Z ZF tranny as the E53 4.4 X5.

Steptronic Slam is Back - 5 Series Forums

This morning I took my car out with an engineer from ZF (who make the transmission) heis seconded to BMW UK to troubleshoot transmission issues.

He connected up a diagnostic kit to the plug in the drivers footwell to monitor the tranny whilst I drove.

We were able to reproduce the 'slam' to order by slowing to about 3 mph gradually and then just before coming to a halt, accelerating fairly briskly.

Almost every time the revs went up and after a delay the car picked up the drive and shot forward.

We could also reproduce another behaviour. When going down a steep hill, causing acceleration due to gravity with foot off throttle, touch and release the brakes. The car downshifts 2 gears, giving high revs, then accelerate again and you get quite harsh upshifts.

His explanation of the 'slam' was as follows.
The transmission is working 'normally'. The shift point is set up with a stop/go system so that as you drive in traffic the car does not drop below 2nd gear. This enables a smooth progress without unnessecary shifts into 1st. The normal pick up with gentle acceleration is easily achieved in 2nd.

The consequence of this set up is that if you suddenly ask the car for high acceleration levels it detects that it cannot achieve this in 2nd and selects 1st with a consequent delay. This has been measured by ZF as about 0.75 seconds, though he accepted it often feels a lot longer.
I pointed out that when pulling out into traffic which is travelling at 50mph, on oncoming car travels at 75 feet per second, so 0.75 of a second delay is not good news.

The only solution to the issue is to reset the shift points so that the car always selects 1st when the speed drops, this however would mean a huge number of 1>2 > 1 shifts in stop start traffic giving a poor ride and the risk of harsh low speed shifts.

The problem is exacerbated in larger diesel engines due to the high torque and the slight turbo delay.

The same process is present in petrol engines but is felt much less due to the faster response of the engine to the throttle and the lower torque at lower revs. hence it is often viewed as a diesel only problem. The greater the torque the more noticeable the behaviour. This explains why the 530D and 545i and up raise complaints whilst the 520i and 525D seem less prone.

The only way to mitigate the issue is to select DS which forces selection of 1st at low speeds, but be aware that you will feel harsher 2>1 shifts in traffic.

Every 5 series 'suffers' as do Jaguars, Audi's and others but due to different driving styles and road environments, some drivers will notice it more than others. It is especially noticeable if you are a frequent user of roundabouts where you often approach at a very slow speed the accelerate without coming to a full halt.

The downhill behaviour is due to the software detecting acceleration whilst also detecting a braking signal. It interprets this as brake failure and, as a safety system, initiates downshifts to provide engine braking.

The bottom line is that currently there is no 'solution' to the 'slam' issue, there is no software update beyond 17.10 that will have any direct effect on the tranny behaviour, though he does not rule out that at some time in the future there may be changes. There is nothing currently on the radar.

[bmwmmn]

Greatly appreciated "rayxi" for this input form other forum. ... will definitely try to use recommended sequence of selecting manual mode to engage 1 gear and shift it back later on into auto. mode. I hope my transmission will adapt to this.

Cheers

[mrtm2008]

I already do this with my wife's X5 4.4i, expecially on cold start up. I manually shift until I see the oil temp is at or close to normal running temp.

Originally Posted by bmwmmn

Greatly appreciated "rayxi" for this input form other forum. ... will definitely try to use recommended sequence of selecting manual mode to engage 1 gear and shift it back later on into auto. mode. I hope my transmission will adapt to this.

Cheers

[admranger]

Originally Posted by rayxi

Did a bit of digging and found this explanation of the issue. The poster owns a 535d which has the same GA6HP26Z ZF tranny as the E53 4.4 X5.

Steptronic Slam is Back - 5 Series Forums

What a load of crap from the ZF engineer.

The Allison transmission on my old Chevy diesel dually and diesel pusher motorhome never had this problem. Clearly a design/software flaw and they went to the "they all do this" response as their answer. Horrible response. I had the software update and after that I had the biggest slam ever in a parking garage. It was so bad my passengers thought we'd been rear ended by a truck or something. It was awful.

[sunny5280]

Originally Posted by admranger

What a load of crap from the ZF engineer.

The Allison transmission on my old Chevy diesel dually and diesel pusher motorhome never had this problem. Clearly a design/software flaw and they went to the "they all do this" response as their answer. Horrible response. I had the software update and after that I had the biggest slam ever in a parking garage. It was so bad my passengers thought we'd been rear ended by a truck or something. It was awful.

I'm with you. My 2000 4.4i drove without a single problem for six months. Then the transmission began to act up even though my driving habits remained the same. I took it to my indy and he replaced the valve body and the problem disappeared.

I'm surprised to see after so many years this is an issue for which there appears to be no consistent solution. I would have thought the underlying cause would have been diagnosed by now.

[MADT]

Just spoke to the BMW engineer I have had dealings with in the past and he was quite helpful as he usually is.

He was quite aware of the issue and said that it has been addressed in a software fix. A routine ECU update may not work as the updates may not go far enough without being purposely influenced by the tech who knows what they are doing.

Mine is booked in and he will talk them through it and then reset the adaptations and he said it should fix the issue, otherwise the valve body may need replacing.

Ill let you all know of the outcome

[phil47]

Originally Posted by dcashion

Just spoke to the BMW engineer I have had dealings with in the past and he was quite helpful as he usually is.

He was quite aware of the issue and said that it has been addressed in a software fix. A routine ECU update may not work as the updates may not go far enough without being purposely influenced by the tech who knows what they are doing.

Mine is booked in and he will talk them through it and then reset the adaptations and he said it should fix the issue, otherwise the valve body may need replacing.

Ill let you all know of the outcome

Good luck with that, I suspect it will help. The material Rayxi posted is very interesting...particularly the date of February 2006. Sure enough it was approximately December 2006 that I was made aware of the just released software update to v23 that seemed to fix the problem for a number of us. I went through the reset process last night and am waiting to see if the problem reoccurs. Here's hoping I get another 3 years of trouble free shifting.