BMW SMG Gearbox

"Erik" wrote

There have been 3 BMW SMG gearboxes. You need to specify which one.

The general sense I've seen is that the one in the M5 is the best, but all of them are barely acceptable for in-town or stop-and-go driving, and that manual control is much preferred to the auto modes.

FloydR

I can speak an opinion in the case of the new, E60 M5 SMG. I had two different '06 cars and reluctantly got rid of them.

The SMG's "automatic" mode is worthless, IMO. Jerky and not pleasant at all to drive. The car performs very well shifting in the "manual" mode, but unfortunately it has been a source of many problems with an inordinate number of owners getting the infamous "Red Cog of Death". The problem sometimes resets itself, but often the gearshift locks up and the car ends up being delivered back to the dealer on a flatbed. BMW has been plowing along, replacing components but the problems continue. This version of the SMG is soon to be replaced with a double clutch designed system and hopefully it will cure the one major weakness of this otherwise great car.

RCE

As far as clutchless manual transmissions go, the BMW ones are pretty good from E46 onwards (E36 was too slow).

However, my opinion on clutchless manuals? I would much prefer a normal manual transmission. I really don't understand why people buy vehicles with this type of system. Fashion maybe? Drive one and they are not all they are hyped up to be.

General sense? Just curious, have you driven one?

I have the SMG II in my E46 M3. I like it a lot. The manual mode is great fun and very crisp, without killing my left leg :).

The auto mode is excellent. I have found in my conversations that negative opinions are mostly from people (hey, I can generalize too) that expect it to be an automatic (i.e. torque converter). It's not. You have to be aware that it is a manual transmission. It will shift at bad times, if you're not careful. It will roll backwards on a hill.

All that said, you have to drive it yourself. The challenge is that it takes a couple weeks to really understand it. Before that, it will be jerky and a real pain -- until you're good at it. Then you'll likely love it.

That's ridiculous. I have one because

1) I hate to clutch. Hate it 2) Like occasionally using the auto mode in traffic.

You've obviously never driven a twin layshaft type as fitted to Audi, etc, and soon to be fitted by BMW. This is also a synchromesh (*not* manual) gearbox which makes a pretty good fist at being as smooth changing as a torque convertor type when in auto mode.

Obviously the superior design.

It is, but a great deal more expensive to make. I dunno why the single clutch type are always so poor (rough) in manual mode as a decent driver can change gear pretty smoothly on a manual box so there's no intrinsic reason why a computer can't ape that. Perhaps the slower gearchange sequence needed isn't favoured by the development engineers. ;-)

I understand the DSG is superior, but the SMG isn't rough. The shifts are very smooth.

Oh, and synchromesh has nothing to do with manual vs. automatic. It is still a manual. If it doesn't have a torque converter, so it isn't an automatic.

But this can devolve into a religious argument. Some like it, some don't. I do.

Tom

The "religion" part is whether SMG is an automatic transmission or a manual transmission.

Simple answer: No.

Extended answer: It's neither.

Not any of the ones I've tried. I'd be ashamed of my gearchange and clutch skills if I changed as roughly when driving slowly.

I take it you don't understand the meaning of the word? Was the original GM Hydramatic from the '50s not an auto because it didn't have a TC? The various M-B boxes either? And how about CVTs? The original DAF had only forward neutral and reverse. Was that a manual too?

My feeling is some who buy SMG think they're buying a race car transmission which can't be therefore an auto. But if it is capable of changing gear on its own it is by *definition* an auto.

It's an auto with a degree of manual control. Is it impossible to stall the engine? Impossible to select a gear at too high/low a speed for the engine? Can you select drive and the car go from rest to top speed with no involvement from the driver as regards clutch or gearchange? If the answers are yes it's an auto. Whether or not it has a torque convertor is irrelevant.

Then really you need an automatic, not a clutchless manual.

You have it backwards, but that's the religious part. It's a manual with a degree of automatic control. It has a clutch.

Wow, you're an ass.

No, I don't. I need a clutchless manual. I like to shift. I don't use it in auto mode except very rarely.

Dave, I give you credit for tenaciously maintaining your opinion that a SMG is an automatic transmission, semantics or not.

Unfortunately, most of us that have owned one agree with the BMW engineering position that it is an automatically controlled *manual* transmission.

RCE

You can manually shift with an automatic transmission too.

What clutchless manuals do is to reduce the amount of control of the vehicle that you have, as there is a direct drive that you have no control over and can't intervene. It is a road car at the end of the day, not a rally car.

I will give you one example for 'normal' driving, you are at a round-a-bout with a lot of traffic coming round it, you need to accelerate quickly to get out in the traffic, but then need to slow down to go around the round-a-bout. It is not possible to dip the clutch for a smooth transition from accelerating hard, to backing off and braking, instead, all your passengers need neck braces.

For what it's worth, I don't like the paddle shift either, unless in a straight line. If I was forced to have an SMG over a manual, I would use the gear stick for the majority of the time.

Dave, Dave, Dave... I have seen the light and I am enlightened. It's an auto with a degree of manual control. Its a manual with a degree of automatic control. It slices, it dices, it makes julienne fries. It's the Popiel Pocket Transmission...

By the way, regardless of what it is, I have no use for it.