BMW/VW transmission query

[Dangerous Dan]

This is something that has been on my mind for a few days now...

Why does a company like BMW persist with a (albeit absolutely sublime) traditional automatic transmission whilst the VAG group has pretty much moved to a dual clutch system (DSG) in most of their models? Why hasn't BMW jumped on the DSG band wagon.

[Toaster Pilot]

BMW have a DSG-esque system in some cars don't they? SMG or something?

[Pistom]

I drove an A6 with the step less system. If that's what Audi does then give me a conventional auto and day.

The Audi system is second only to Smart as being the most horrible box invented so far.

[cuprabob]

Pistom said:

I drove an A6 with the step less system. If that's what Audi does then give me a conventional auto and day.

The Audi system is second only to Smart as being the most horrible box invented so far.

Sounds as if you were driving a CVT and not a DSG

[davepoth]

Dangerous Dan said:

This is something that has been on my mind for a few days now...

Why does a company like BMW persist with a (albeit absolutely sublime) traditional automatic transmission whilst the VAG group has pretty much moved to a dual clutch system (DSG) in most of their models? Why hasn't BMW jumped on the DSG band wagon.

Because a DSG box is expensive and complicated compared to a torque converter box. They also have more bits to go wrong, and the 8 speed box that they're now using is very close to the DSG boxes in terms of economy.

[Ed.]

Dangerous Dan said:

This is something that has been on my mind for a few days now...

Why does a company like BMW persist with a (albeit absolutely sublime) traditional automatic transmission whilst the VAG group has pretty much moved to a dual clutch system (DSG) in most of their models? Why hasn't BMW jumped on the DSG band wagon.

Vag is the odd one, they use a conventional auto, wet and dry clutch DSG's, CVT and a robotised manual but they do sell lots of different cars. ZF, Aisin and Borgwarner design most of them for the manufacturers in any case..

[b0rk]

VAG are unusual in that they still build their boxes but buy in the shifter/clutch pack, BMW buy in their boxes complete usually from ZF. BMW can only offer DCT's as the gearbox OEM's develop such boxes.

The latest generation of VAG DCT's are good for upto 600N so most of the SMG's, CVT's, automated manuals will disappear over the next few years.

[Fox-]

Dangerous Dan said:

This is something that has been on my mind for a few days now...

Why does a company like BMW persist with a (albeit absolutely sublime) traditional automatic transmission whilst the VAG group has pretty much moved to a dual clutch system (DSG) in most of their models? Why hasn't BMW jumped on the DSG band wagon.

They have - BMW have DCT gearboxes available now - both in M and non M form.

The reason why BMW persist with traditional automatics is that for the job of being a 'traditional automatic', DSG simply doesnt compare to a torque converter. DSG has its strengths - it's far more suited to something like a sporty hatch than a traditional gearbox is for example - but in a big executive car you want a torque converter not a DCT.

But if you DO want a DCT its been available since about 2009.

[F i F]

Fox- said:

They have - BMW have DCT gearboxes available now - both in M and non M form.

The reason why BMW persist with traditional automatics is that for the job of being a 'traditional automatic', DSG simply doesnt compare to a torque converter. DSG has its strengths - it's far more suited to something like a sporty hatch than a traditional gearbox is for example - but in a big executive car you want a torque converter not a DCT.

But if you DO want a DCT its been available since about 2009.

Interested to know why you say TC better than DCT for big exec cars. OK the lack of torque capacity has been one reason until recently, but have been driving DCT and PDK for a while now, and when go back to an old torque converter auto they have seemed very agricultural. The changes on DCT are in the main smooth as silk and very well timed ime.

[Fox-]

I have never driven a DCT/DSG car that was quite as seamless and smooth shifting as a torque converter equipped automatic. But I have never driven a TC auto that was quite as responsive with such quick changes as a DCT/DSG - so they are very much two different techs for for two different tastes..

[Garvin]

BMW have a DCT transmission - I have one in my current Z4. My previous TT had an DCT (S-Tronic) transmission. They are both very, very similar the only real difference is that the VAG version is quick shifting (and very seamless) in normal and sport modes, whilst the BMW version is 'lazier' in normal mode (trying to emulate the feel of a conventional 'slushmatic' perhaps?) but sharpens up considerably in sport mode. The VAG version is more seamless in its gear changes but the BMW is better at being in the right gear, the TT could be caught out occasionally in this respect (but both should never be caught out in manual mode!). The paddles are set up differently - push either paddle to downchange, pull to change up in the BMW; pull left paddle to downchange, pull right paddle to change up in the VAG version.

Personally, I will now never consider having a car without a DCT - they take some learning to get the best from them but, IMHO, really do have the advantage over both a conventional manual (unless you like the involvement of left leg, left arm whilst driving) and a conventional automatic.

[CraigyMc]

b0rk said:

VAG are unusual in that they still build their boxes but buy in the shifter/clutch pack, BMW buy in their boxes complete usually from ZF. BMW can only offer DCT's as the gearbox OEM's develop such boxes.

The latest generation of VAG DCT's are good for upto 600N so most of the SMG's, CVT's, automated manuals will disappear over the next few years.

VW/Audi/Skoda/Seat's DSG boxes are bought in from borg warner (who call them "DualTronic"), and LuK (who call theirs "PSG").
I'm not sure why you think otherwise.

BMW's E90 M3 M-DCT clutchpack is also from Borg Warner, although assembly of the overall box is by Getrag.

As a matter of fact, I can't think of a single car manufacturer who actually produces their own gearboxes for series production, in the modern world.

C

[tgr]

Don't merc still do their own? I remember at one point Jag had to have merc auto gearboxes fitted because the torque of their (supercharged I think) engine was beyond the tolerances of their normal gearboxes

Give me a manual any day - not because this is pistonheads, but because I don't believe TC, DSG, DCT or PDK are built to last very long and will need very expensive repairs/replacement in due course

[Deva Link]

tgr said:

Don't merc still do their own?

Yep.

The new B Class, just starting to be sold now, has a DCT gearbox. The SLS had one a couple of years ago.

[CraigyMc]

tgr said:

Don't merc still do their own? I remember at one point Jag had to have merc auto gearboxes fitted because the torque of their (supercharged I think) engine was beyond the tolerances of their normal gearboxes

Give me a manual any day - not because this is pistonheads, but because I don't believe TC, DSG, DCT or PDK are built to last very long and will need very expensive repairs/replacement in due course

I'm with you on the "give me a manual box" thing. I want to drive, not just "operate the vehicle" if that makes sense. I'm sure there are old timers kicking about who miss being able to advance their ignition manually just as I'll eventually miss manual gearboxes.

Jag (in common with a fair number of other manufacturers in that sector) tend to use ZF. I'm not sure of their entire range though.

Merc's 8 speed is from ZF, though you're right: they do a lot of stuff in-house (the "722" gearboxes).

I just checked on ZF's website and apparently they've done a 9-speed auto for (BMW) mini which hasn't seen the light of day yet. Surprised they'd put stuff online like that but there you go!

C

[CraigyMc]

Deva Link said:

tgr said:

Don't merc still do their own?

Yep.

The new B Class, just starting to be sold now, has a DCT gearbox. The SLS had one a couple of years ago.

The SLS 7-speed is a bad example of Merc doing their own gearbox given that it was made by Getrag.

C

[Deva Link]

CraigyMc said:

The SLS 7-speed is a bad example of Merc doing their own gearbox given that it was made by Getrag.

C

Sorry, I didn't mean to link them as if they were the same gearbox - they're completely different.

[tgr]

CraigyMc said:

Deva Link said:

tgr said:

Don't merc still do their own?

Yep.

The new B Class, just starting to be sold now, has a DCT gearbox. The SLS had one a couple of years ago.

The SLS 7-speed is a bad example of Merc doing their own gearbox given that it was made by Getrag.

C

Which is owned by Ford if I recall correctly. Not that this means it's a 'Ford' gearbox of course

[Garvin]

tgr said:

........ but because I don't believe TC, DSG, DCT or PDK are built to last very long and will need very expensive repairs/replacement in due course

Why so? They are software controlled - software doesn't 'go wrong' (it may be designed wrong but doesn't wear out in use) it's usually the hardware that the software runs in that has problems. These boxes pre-select the gear on the 'non-used shaft' so it's not under any stress so it's difficult to abuse these transmissions, unlike manual boxes. The clutches are also software controlled so not really susceptible to human error (too many 'dumped' clutches at high revs or too much induced slip). It's down to the controller/selector and whilst the early VAG boxes had some trouble with their 'mechachrome' units they are, generally, very reliable.

[F i F]

Garvin said:

tgr said:

........ but because I don't believe TC, DSG, DCT or PDK are built to last very long and will need very expensive repairs/replacement in due course

Why so? They are software controlled - software doesn't 'go wrong' (it may be designed wrong but doesn't wear out in use) it's usually the hardware that the software runs in that has problems. These boxes pre-select the gear on the 'non-used shaft' so it's not under any stress so it's difficult to abuse these transmissions, unlike manual boxes. The clutches are also software controlled so not really susceptible to human error (too many 'dumped' clutches at high revs or too much induced slip). It's down to the controller/selector and whilst the early VAG boxes had some trouble with their 'mechachrome' units they are, generally, very reliable.

The issue that worried me about DCT boxes at first was the way they used the clutches to simulate torque converter creep. I could see how wet clutches could stand this, and I'm still a bit worried about dry clutched versions. No problems experienced yet and we've put a fair few miles on. Will they still be OK at 150,000 miles? Who knows but I bet a manual clutch would have gone, and I'm sure the software does rev matching and sympathetic clutch engagement better than I can day in day out to my shame.

The one issue I really do not like on DCT is reversing downhill into a tight space. The transmission is trying to creep, but as it's a tight space you're left foot braking, or even just braking to check the motion. The braking causes the clutch to disengage, so you lift off the brake, for the clutch to engage again as it wants to creep. But it's downhill so you are straight back on the brake to keep it in check, and rinse and repeat. It's all very inelegant and sometimes is not that smooth. Frankly I can reverse under far more inch perfect control with a manual box and a clutch pedal.