The Automatic Gearbox And Its Failings

[DonkeyApple]

Hasbeen said:

I do a fair bit of driving on nice country roads, with many up hill tightish, [70 to 90 Km/H] corners in up hill roads. Auto's used to really annoy me, when you would be accelerating into such curves, & have to lift off as you arrived at them.

The damn things would of course change up, then make a hell of a meal finding the right gear to accelerate out of them. Yes you could manually slot a gear, but autos leave a lot to be desired when manually selecting gears, & I can't stand sequential things.

I was surprised when I discovered my ladies Mazda 2 had tried to overcome this problem, I did not expect it in a shopping trolley. When accelerating up hill it would hold what ever gear it was in, when you backed off for a few seconds. In fact you could not get the thing to change up in this situation, until you were over 6500 RPM, with a lot of throttle on. If you lifted off at say 4000 RPM, the damn thing would actually roll to a stop without changing up.

I gather they have got this better organised in the latest ones. Nice to see them trying.

The moment boxes became electronic the real problems started going away. We got much faster changes and they began measuring a series of variables to predict what was expected of them. In the early days they tended to be a bit crap and did weird things as they guessed wrong but in the last few years they have changed dramatically with the improvements in processing power and mapping more than anything. A modern, well programmed auto is a phenominal bit of kit.

[cerb4.5lee]

b0rk said:

cerb4.5lee said:

It not changed in my experience we have a 2012 Audi TTS with the twin clutch gearbox and it seriously reminds me of old school Turbo engines because you literally put your foot down wait a bit then it rockets off because its such a laggy engine and I would be interested to know if its the same for the manual version though.

If you've got the box in drive I can quite understand the "lag" issues as the box will be deliberately keeping the rev's down to maximise fuel economy and thus the engine will be off boost or at very low boost. The gear ratio's allow for 35MPH in 5th. In S mode it should be far more urgent and generally free from lag.

The manual version will really depend on how you drive it, if you follow the gear selection guidance then yes it will feel very laggy. Drive it normally ignoring the guidance and it won't but you'll sacrifice fuel economy somewhat.

You make a very good point and it is less laggy in sport but still noticeable though but in many ways I quite like its laggy nature as it reminds me of the old days a little and even as standard it runs a fair bit of boost so it will inevitably be a little laggy I think.

[Limpet]

I've just done 2700 miles in two weeks in an Audi A4 2.0TDI Multitronic. And I enjoyed it. Not fun in the slightest, but truly a transmission you don't notice. In any normal accelerative situation, you push the accelerator pedal, the revs settle between 1500 and 2500 RPM where the diesel lump is little more than a mellow background hum, and the car goes with no fuss, and very little noise in one seamless haul. My only gripe was the engagement of the clutches when you want to creep very precisely. Such as when boarding the Eurotunnel shuttle for example. Otherwise, it did Alpine passes, 120+ mph Autobahn stretches, Munich roadworks hell, and fiddly mountain roads around Lake Garda, and behaved faultlessly.

I know these have a properly shocking reputation for reliability, but I don't recall many engine and transmission matches that worked better. Also says a lot for its calibration that it helped a relatively weedy 2.0 diesel engine feel more than up to all of the above, even when fully laden.

Edited by Limpet on Tuesday 26th August 16:02

[anonymous-user]

Limpet said:

I've just done 2700 miles in two weeks in an Audi A4 2.0TDI Multitronic. And I enjoyed it. Not fun in the slightest, but truly a transmission you don't notice. In any normal accelerative situation, you push the accelerator pedal, the revs settle between 1500 and 2500 RPM where the diesel lump is little more than a mellow background hum, and the car goes with no fuss, and very little noise in one seamless haul. My only gripe was the engagement of the clutches when you want to creep very precisely. Such as when boarding the Eurotunnel shuttle for example. Otherwise, it did Alpine passes, 120+ mph Autobahn stretches, Munich roadworks hell, and fiddly mountain roads around Lake Garda, and behaved faultlessly.

I know these have a properly shocking reputation for reliability, but I don't recall many engine and transmission matches that worked better. Also says a lot for its calibration that it helped a relatively weedy 2.0 diesel engine feel more than up to all of the above, even when fully laden.

Edited by Limpet on Tuesday 26th August 16:02

I must admit I like those, it's like having a car with one gear that's always the right gear. Perfect in a boring snotbox.

[Patrick Bateman]

Bit of a thread revival.

Getting more used to the autobox in my 7 series (e65 745i) and just curious about some of the 'characteristics'.

I've noticed a couple of times when flooring it that the revs don't always seem to move in proportion to how the car is behaving. The first time I noticed it was a few weeks ago when flooring it in 3rd in manual mode and as I was accelerating at full throttle I noticed the revs stayed on 3k for a good few seconds and didn't budge.

Tonight at one point as I was gently accelerating I saw the revs actually dropping for a couple of seconds at that moment. I know it's an old 6 speed gearbox and nothing like the latest 8 speed offerings but I'm not sure if this is a sign of something untoward in waiting or if the revs shown with an autobox can be a bit misleading?

[E65Ross]

I hate to say it Patrick Bateman but it never did that under my ownership.

[Patrick Bateman]

E65Ross said:

I hate to say it Patrick Bateman but it never did that under my ownership.

Tonight was the first time I'd ever noticed the revs dropping. Also had a play about in the manual mode while flooring it and all seemed fine going up the gears.

It's hard to know what to expect though having never driven another. Just the simple things like how smooth should a manual change be if at say 30mph and going down to third then second? Maybe I had my expectations high but it just seems a bit dim-witted.

Edited by Patrick Bateman on Monday 22 January 19:57

[cerb4.5lee]

Patrick Bateman said:

Maybe I had my expectations high but it just seems a bit dim-witted.

The gearbox just isn't really that great imo, I found it dim witted in both my X5 4.8iS and E90 330i...strangely though I found it suited my E90 330d a little better...it really is a poor match to a petrol engine for some reason.

I found it's best just to take a steady Eddie approach with it, because it doesn't really respond that well when pushing on. The current ZF8 has moved things on a fair bit...but that's not without its faults either.

[Patrick Bateman]

Looking into this a bit more I wonder if it's more the cold start procedure the car follows to get the oil up to temperature, during which the torque converter isn't actually doing very much.

[anonymous-user]

Patrick Bateman said:

Looking into this a bit more I wonder if it's more the cold start procedure the car follows to get the oil up to temperature, during which the torque converter isn't actually doing very much.

Every modern auto delays TC clutch lockup and changes up later when cold to try and heat the oil up faster. The behaviour will almost certainly be described in the service books for the car, it is for Jaguars using the rather overrated ZF 6 spede box.

They don't just lock the converter on or off anymore, they use controlled slip so the apparent stall ratio of the TC seems to change depending on what it's up to. Even the mediocre AW 5 speeder in my old V70 did it. I drove an XF with the ZF8 and that seems to unlock the TC to change gear and almost immediately lock it back up again when the car is warm.

[ruggedscotty]

getting used to a 7 speed auto in an A6.

managed to average 55mpg on the way to work today, mind you 38 on the way home with the traffic crap. dsg box and very good at being in the right gear at the right time.

[Patrick Bateman]

dme123 said:

Every modern auto delays TC clutch lockup and changes up later when cold to try and heat the oil up faster. The behaviour will almost certainly be described in the service books for the car, it is for Jaguars using the rather overrated ZF 6 spede box.

They don't just lock the converter on or off anymore, they use controlled slip so the apparent stall ratio of the TC seems to change depending on what it's up to. Even the mediocre AW 5 speeder in my old V70 did it. I drove an XF with the ZF8 and that seems to unlock the TC to change gear and almost immediately lock it back up again when the car is warm.

Paid close attention to the revs this morning. Within the first few minutes of driving I had the cruise control set at 60 and noticed the revs hunting between about 2000 and 2100/2200 a few times while at a constant speed.

After a short stint (less than 30 seconds) of that I joined the dual carriageway and accelerate back up to 60. Now the revs are solid and don't hunt at all.

Normal?

[E65Ross]

Patrick Bateman said:

Paid close attention to the revs this morning. Within the first few minutes of driving I had the cruise control set at 60 and noticed the revs hunting between about 2000 and 2100/2200 a few times while at a constant speed.

After a short stint (less than 30 seconds) of that I joined the dual carriageway and accelerate back up to 60. Now the revs are solid and don't hunt at all.

Normal?

Don't recall having that experience.

[Patrick Bateman]

It only seemed to happen once up to speed. This is all less than 5 minutes after starting the car though.

[E65Ross]

Hmmm, it usually took me at least that to get to a motorway usually so maybe I never noticed it. Just keep an eye on it and see if it changes.