16 replies to this topic

[Sphinx]

Noticed something strange recently regarding the gear changing.

Usually the gear changes take place between around 2500 and 3000 rpm

Doing my usual route down a dual carriage way, was cruising around 30 when the car could make up its mind to which gear it should be in.

It would drop down a gear for about 3-4 secs then back up. It was like saying to me "hmm, I wonder what 30 feels like in 3rd, nah, 4th is better, but then again...

This carried on for a few seconds, by then I cheesed off and put into sport mode and then back into drive and then the everything was ok.

Only happens occasionally, tried a battery reset - but its still the same.

Is it the torque converter playing up?

[BestMotorintheWorld]

I'm interested to hear what you say because this is an issue for which the dealers have no explanation and no cure. My car does exactly the same from time to time and I've just learned to live with it. Shifting to "sport" and back again clears the problem, whatever it is. IMO it's just an electronic/software glitch and nothing to worry about. None of the explanations people have attempted get anywhere near a sensible answer. Don't worry about it. In particular; if it ain't broke don't fix it!

[Sphinx]

I reckon it has something to do with AGS.

have a read of this :

IMPORTANT INFO #1:

'It has no memory - it reacts constantly to whoever is driving the car, and to changes in the driving conditions'

'The four main programs are chosen by the way your are driving from moment to moment. So for example, if you press or lift off the accelerator gently, AGS will chose Extra Economy. More determined pressure or quick release will select Extra Sport instantly'

Which would explain why diconecting the battery has no effect and why my mate ragging my car only had a short effect.

IMPORTANT INFO #2:

'AGS knows when the car is cornering hard, and surpresses gear changes to maintain optimum stability and control'

IMPORTANT INFO #3:

'Find a downhill gradient of at least 10% with a clear section of about 500m. Enter the section at a steady 50mph. Slowly take your foot off the accelerator. The car's speed will start to increase - as it does so, gently touch the brakes - AGS will change from fifth to fourth so that the engine's braking pwoer will help to slow the car down.'

IMPORTANT INFO #4:

'If you have been driving for at least three minutes or have driven at more than 62mph, the stop and go traffic program is available.

To experience this for youself, stop, then move off without applying more than 20% throttle, up to a maximum speed of 20mph. The gearbox will select first gear to pull away. Stop again then repeat. Next time, AGS will set off in second gear to give a smoother start. To exit traffic mode simply apply more than 20% throttle'

[BestMotorintheWorld]

Yup, I'm familiar with all that. But I still say these transmissions develop a mind of their own from time to time. Happily a switch to Sport and back sorts it out nicely.

[Sphinx]

Not 100% sure on this, but I have heard there are 2 memory settings for the AGS.

A short term and long term.

The short term stores the last 50 miles after a battery disconnect.

A long term is dealer reset only.

Have you heard of this?

[BestMotorintheWorld]

Have you heard of this?

I have heard of that kind of thing for electronic auto's but have no knowledge of whether it applies to the Beemer.

My transmission likes to get itself back into the "just cruising" program as quick as it can and defaults to that setting in very few minutes of gentle driving. Equally well it takes very little vigorous use of the accelerator to get it into a "sport" frame of mind, although I usually instigate that program manually when required.

It's a fine transmission IMO.

PS It's best not to use manual downshifting to decelerate the car with engine braking as this can cause premature wear of the transmission bands. Brake pads are a lot cheaper than a transmission rebuild!

[studyolic]

PS It's best not to use manual downshifting to decelerate the car with engine braking as this can cause premature wear of the transmission bands. Brake pads are a lot cheaper than a transmission rebuild!

Are you sure about this? I frequently knock the gearshift into Sport to drop a gear and get some engine braking.

Richard.

[BestMotorintheWorld]

Are you sure about this? I frequently knock the gearshift into Sport to drop a gear and get some engine braking.

Yes, I'm sure. It's the slippage as the gears change which is the problem area rather than the subsequent engine braking itself. You can reduce the effect by "rev-matching" as you change down, just the same as (I hope) you would with a manual transmission. At the end of the day it's not going to kill your transmission overnight but does lead to accelerated wear.

[Sphinx]

I posted the same question over on BMW car forum, and someone said it was down to a sensor, but they cant remember which one it was.

[RockyBalboa-UK]

Rear wheel speed sensor, perhaps?

[Sir Anthony Regents-Park]

I had this with my 840Ci - nothing wrong with it. It's a result of 50+ miles of really laid back driving followed by some 'sporty' demands and the AGS has an "arse/elbow interface problem"

I would recommend going to a gearbox specialist and having the gearbox sump dropped and cleaned out, a new filter screen and fresh oil - you'd be surprised how 'orrible it looks/smells after 60'000 miles. It'll be about £100 and is well worth it. Mine had done 62'000 when my local BMW dealer did the job and it did upshift better.

[Sir Anthony Regents-Park]

It could well be an ABS sensor but to be honest this normally bring up 'TRANS PROG".

[BestMotorintheWorld]

Had a repetition of this one yesterday. Driving south from Leeds the M1 runs slightly uphill. I was on "cruise" at normal speed and the hill caused the transmission to shift down to fourth. Where it stayed. I decided to wait and see how long it would remain in fourth and the and the answer was, for ever! Eventually I had to apply the brakes when coming up behind slower traffic and once the cruise disengaged eveything was back to normal. Guess the computer just gets confused occasionally.

[Sphinx]

Had a repetition of this one yesterday. Driving south from Leeds the M1 runs slightly uphill. I was on "cruise" at normal speed and the hill caused the transmission to shift down to fourth. Where it stayed. I decided to wait and see how long it would remain in fourth and the and the answer was, for ever! Eventually I had to apply the brakes when coming up behind slower traffic and once the cruise disengaged eveything was back to normal. .

Same thing happened to me from a trip down to london on the M40.

car has done 77k now, will look into changing the gearbox fluid.

[catboy]

have you all got 18" wheels by any chance?!..

[Murph]

Removing the battery was an old adage I had heard with my 1997/R 540 (and seemed to work). When I had similar issues to what you describe (gear changes being intermittent), I asked about the disconnecting of the battery, to which I was reliably informed that the model I have no longer works like that (it remembers!). Resetting the adaptions works best but this needs either a $tealer or Indy to do.
Since the gearbox having new oil in mine (and adaptions reset), the car drives beautifully.

[Defector]

I reckon it has something to do with AGS.

have a read of this :

IMPORTANT INFO #1:

'It has no memory - it reacts constantly to whoever is driving the car, and to changes in the driving conditions'

'The four main programs are chosen by the way your are driving from moment to moment. So for example, if you press or lift off the accelerator gently, AGS will chose Extra Economy. More determined pressure or quick release will select Extra Sport instantly'

Which would explain why diconecting the battery has no effect and why my mate ragging my car only had a short effect.

IMPORTANT INFO #2:

'AGS knows when the car is cornering hard, and surpresses gear changes to maintain optimum stability and control'

IMPORTANT INFO #3:

'Find a downhill gradient of at least 10% with a clear section of about 500m. Enter the section at a steady 50mph. Slowly take your foot off the accelerator. The car's speed will start to increase - as it does so, gently touch the brakes - AGS will change from fifth to fourth so that the engine's braking pwoer will help to slow the car down.'

IMPORTANT INFO #4:

'If you have been driving for at least three minutes or have driven at more than 62mph, the stop and go traffic program is available.

To experience this for youself, stop, then move off without applying more than 20% throttle, up to a maximum speed of 20mph. The gearbox will select first gear to pull away. Stop again then repeat. Next time, AGS will set off in second gear to give a smoother start. To exit traffic mode simply apply more than 20% throttle'

Looks familiar!

Just to add, the long term memory is only in respect of clutch pack wear, oil levels etc. Reseting this will actually make it worse AFAIK. The short term memory is the one that affects behaviour.

I'm having issues with the box at present, so much so i'm thinking of swapping for a manual.

With current cash flow issues, i'm going to try the cheaper option of a oil/filter swap and a diff swap to see if i can get it to behave a little better.