Steptronic jerk

On putting the transmission into D or R, a couple of seconds later the car jerks slightly. The handbook says to wait for it before moving and I assumed it was it going into gear. However I discovered the other day
that the car will move forward (or back) almost instantaneously D or R is selected, but you still get that jerk 1-2 secs later even after the car is moving.
So I was curious about that anyway, but more seriously I had it in P or N (forget which) at a slow traffic light and was a bit late noticing it change, so I hurried into D and pressed the go pedal moderately, which if you've driven a 540 you will know is something like being shoved quite gently by a large elephant. The car took off but 1-2 seconds later there was a massive jerk, and a sound almost like a bang.
It seems likely this is the same thing as the slight jerk when the car is at rest or creeping, but magnified by speed/acceleration. The question is, what is it? Is it right? Fair enough if you are supposed to wait for the 'jerk' before moving off, and I should have left it in D anyway, but surely the Steptronic is supposed to protect the transmission from damage.
1998 E39 540iA. I had the ATF changed last week although I'm still concerned about only being able to change half of it because of the torque converter.
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First thing to check is the switch on the brake pedal. On mine, if you move off with the brakes still slightly applied it (sometimes) appears to confuses the transmission and you get a slight thump as it actually starts in third then changes to first when you release the brake. If you left foot brake you might be unconsciously be doing this. I dunno how obvious this starting off in a higher gear would be on a V-8, though.
However:-
IIRC, on a ZF HP5 there are 7 clutches of various types. When you select a gear from neutral more than one has to change state. The timing of this sequence is I think still controlled by hydraulics. So could be a valve or clutch sticking.

There's really little difference between Steptronic and drive in this respect. The timing of the various clutch sequences doesn't alter. Could be your transmission is actually partially engaging two gears at once - known as tie up.

It's a difficult one. Most transmission specialists simply do a full re-con on a box due to the labour cost in removal and stripping down which is far greater than any likely parts cost. It's possible the valve tray can be easily removed with the transmission in situ and cleaned/checked. Not so with a clutch.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Hi Dave, thanks for the reply.
Dave Plowman (News) wrote:

Is that the same switch for the brake lights?
It seems to start in second when it's raining. Don't ask me how it knows. Or perhaps it decides you are not in a hurry. You can only really tell by flooring it, and then it changes down into first in an amusing way.

I phoned a local BMW specialist and he reckoned it was all normal. He said the car can move forward/backward the instant you engage D/R because it's engaged mechanically by the lever. He said what happens a second or two later, the slight jerk (when stationary or creeping) or nasty thump (when accelerating), was the solenoids kicking in. I asked what this meant, what the solenoids did, and he said something about the fluid. I wish I knew more about how these worked.

Sorry I meant Steptronic as in the system in general. I wasn't using the manual mode. I just thought with all those electronics it would prevent you from damaging it. It's true the manual does say to wait for the jerk before moving off, but still.

Seems OK apart from this one thing, and I'm still not sure if it's a fault or user error.
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To be perfectly honest I've not looked but my guess is no.

Right. I've not driven a 540, so can't comment. Is the handbook no help? It's not that brilliant for mine.

Sounds like he could do to learn too. ;-) My faith in finding a BMW dealer who is both honest and knowledgeable isn't great.
I've got a fairly decent auto specialist close by who could help - they actually re-con the boxes on the premises. But that's probably no help to you.

That applies to any auto, though, and always has. Although they can stand a lot of abuse.

Really needs someone with a 540 to comment. Doesn't sound right to me, though.
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Dave Plowman (News) wrote:

I'll try moving off with the brake on lightly and see if it does the same as yours.

Probably the same book. The only relevant bit is where it tells you to wait for the "slight jerk" after engaging drive and before moving off. Obviously, I disobeyed that. Does yours do the jerk thing as well and, if so, how long after selecting drive and how noticeable is it? Mine is enough to rock the car slightly with the footbrake on.

He seems pretty knowledgeable so far, but I'm inclined to agree that he really didn't know exactly what he was talking about on this occasion.

It's actually working fine, for now at least, and now I know not to accelerate the instant Drive is engaged. No problem. The issue really is whether there is some developing fault that will become a problem in the future. Basically I just want to know what the thump was.

Not many about. BMW dealer was useless when I asked them about something. "We hardly ever see those". Probably because the journalists at the time all said the 528 was better. :-)
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It probably moved off in direct drive (third or fourth, but it would depend on the box) before the correct bands engaged for first or second. As you had far number revs on there would be a quite a lot of inertia in the sun and planet arrangement and this would give your jerk.
If you jump from reverse to drive at say 3,000rpm (as I did once when distracted by a burglar trying to decapitate me with a machete) then there will be a huge jerk and you will break the gearbox!
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R. Mark Clayton wrote:

I once thought I was in manual mode but wasn't and shifted up (to neutral) at about 5000rpm and I felt like a huge jerk.
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In the old days this would have done for the engine (as did shifting down at too higher speed), but you were probably saved by a rev' limiter.
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The rev limit on older engines was generally set by valve float if mechanical tappets or pump up if hydraulic. This wouldn't protect an engine from being over speeded by changing into too low a gear, though.
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wrote:

Actually, some of the US automatics had downshift protection as early as the 1950's. IIRC, my dad's push-button shift Torqueflite '57 Desoto would downshift to 2nd at speeds over 35 when the "1" button was engaged. And if the Reverse button was pushed in at speed on our '60 Rambler ("Flashomatic"?), the transmission shifted into "Low" range - initially 2nd gear and then 1st. When the car finally came to a stop, it would shift into reverse.
Of course, there was no such protection for similar stick shift stupidity.
Tom K.
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speed plus fluid coupling which dated back to the early '50s. 3rd gear wouldn't allow you to exceed maximum revs (about 4000. ;-)) but 2nd was unprotected.

No. And I wish the Steptronic had no 'protection' either. The last 5 speed ZF I had in an E34 didn't, and with a conventional selector was easier to be stupid with the gears. So I'm not sure why the Steptronic needs to have an override at both ends of the scale in every gear.
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Dave Plowman (News) wrote:

To make an effective manual mode would require a lot more than just removing the overrides. My personal gripes are that I would like to see it display what gear it was in always, not just in manual mode, and there should be a way to put it in manual mode without having to change a gear to do so; and, if in 5th, going to manual automatically means dropping to 4th whether you want to or not, which is stupid. Apparently some cars have a button to put them straight into the lowest gear and that would be extremely good.
I had a blast round an empty road one night and the auto was crap, the manual mode was much better. 99% of my driving is not of that type and the auto is better. The other use for manual - and this is where the overrides are useful, given that it does not deign to tell you what automatic gear it is in - is to knock the lever across and push it back 3 times which is guaranteed to put you in the lowest gear ready for an overtake you think you might be able to to in a short time. If OTOH you accelerate without having anticipated it the auto mode is far quicker than manual mode or a conventional manual box.
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Dan Buchan wrote:

Putting it into *sport* drops it down a gear (in most cases), you only have manual when you then move up or down. If you're in 5th and you want to stay in 5th then move across to sport then immediately push the stick up.
I know the 'box is suposed to be adaptive but the other thing I'd like is a manual override.
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adder1969 wrote:

I know and I've done it but you need to know you were in 5th and it's tedious. To go manual you have to go sport and then change gear. But you might not want to change gear yet.
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Jaguar appear to have managed it with the same make of box - although newer. It's said to be as fast as an SMG type.

My guess is that the majority of owners who buy autos don't care what gear it's in. And a constantly changing display might be distracting or annoying for those. Could easily be a software option, though.

I can't see flicking the lever over is more difficult than pressing a button - easier probably given the gear lever is always to hand.

Surely the idea of the sport setting is you want more performance on tap? Fifth is an overdrive gear designed for economy.

Like all these things it might be finding the button. There is already a problem making buttons convenient for various tasks - especially a little needed one. I suppose you could have programmable ones on the wheel.

It's always going to be a compromise given different tastes. Personally I'd be happy if Steptronic always gave you the gear you've selected and held it regardless - like a true manual. But then in the US they'd get sued for having an auto that allows the engine to be wrecked or other nasties.
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Dave Plowman (News) wrote:

You have to change gear though, else you're in sport mode not manual. You have to flick it across and then change gear.

It should be configurable, basically. It wouldn't be hard. Option to turn on/off the automatic up/down changes, that sort of thing. I'd also really like it to beep when it denies a gear change, so you know; ideally, to prevent the lever moving if the gear is not available. The way it shows the gear you selected, then flicks back again, is not helpful if you are driving in a sporty way.
I would not like the ability to force it into any gear though. With a manual box you feel it, going into the wrong gear would be like harming yourself, but with push-button-type action it would be too easy.
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adder1969 wrote:

I once shifted from first to second in a Jaguar XKR. Except I didn't, it was an automatic box, and it went into Park at 30 miles an hour. Well it did look awfully like a manual gear stick.
At least the BMW is fool proof enough to mostly prevent that kind of thing.
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R. Mark Clayton wrote:

It seemed to pull away too quickly for third or fourth. When it went bang it was almost like something locked up. It didn't feel good at all, but even with my paranoia I can't detect any damage from the way it drives.

Sounds like fun. Did you manage to kill him?
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No more of a close shave the other way (machete was blunt and he had a poor angle on the side window, so did not break it).
He was convicted and managed to pay off the compensation over 13 years!
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