Z4 automatic vs. stick

Have you any experience of decent autos? Not being funny, but the SMG isn't in the same class, smoothness wise. And I've driven a recent M5.

In my opinion the "automatic" or "D" mode in the new, E60 M5 is worthless. Shifting manually with the SMG III takes some getting used to but in S5 and S6 modes, it is very smooth and fast.

I recently found out that you can re-calibrate the amount of clutch slip in the M5 (or M6) with the SMG. You drive at least 20 mph ... put the gearshift in neutral so you are coasting and pull up on both paddle shifters. This procedure is recommended whenever you change tires also.

Eisboch

You want it to be as smooth as an automatic? Then buy an automatic. That's not what it is.

And yes, I've experienced a decent automatic. The one in my 540 isn't bad

My Z4 did have a different SMG - There were no options other than the sport button. I think the SMG used in the M3 is much more advanced.

In auto mode, yes. Different when doing the selection yourself and in a hurry. The two aren't mutually exclusive - Audi manage it. As will BMW when they adopt a twin clutch SMG shortly.

If it can change gear without any action on the part of the driver, it's an auto. There is no argument possible about that. An auto isn't defined by the presence of a torque convertor.

Guess we'll just have to agree to disagree.

Could be. The SMG in the Z4 is actually an SSG, an Italian-made less robust version of the SMG used in the M-class cars. epbrown

-- "Everybody wants a normal life and a cool car; most people will settle for the car." Chris Titus

Dave, you can take that position if you like, but why does BMW (and others) offer three different transmission types for the Z4?

Manual Automatic SMG

Eisboch

Because the SMG isn't sufficiently developed to replace a conventional auto. Nor does it give the same driving satisfaction as a true manual. Things may change, though. If you require a 'clutchless' change with total control over the gears, both automated synchromesh boxes and torque convertor autos are improving all the time. I'd not take a bet which will win - although my money says the TC auto since it's intrinsically more reliable.

I would debate the reliability point of a traditional TC/auto with planetary gears, since they have far more parts (mostly bearings, bushings and clutches) than even an SMG. More parts, more things to break.

FloydR

Not that I'm a fan of TC transmissions, but there is something just inherently cool about a planetary gear set. Just a simple arrangement of a few cogs that stays fully meshed all the time, yet it gives you two forward speeds and reverse simply by holding a different part of it still. It's almost like god invented it because he knew it would come in handy when we got around to making cars.

I've mentioned it before, but I've often wondered why no one ever put a friction clutch in front of one instead of a torque converter.

I agree with you about the TC. By design, it allows higher torque application without ripping itself apart.

Eisboch

Because the TC will handle a heck of a lot more torque application. It "gives" where the friction clutch wears out.

Eisboch

Mechanical failure in an epicyclic gearbox is rare. True the clutches can and do wear, but so do those on a servo operated synchro box. As do synchro cones etc - especially with the hammering they get on an SMG.

Some of us buy fine automobiles because we've reached a stage in our lives where "fine" is more imporant than other stuff. When one reaches that point, one buys what they want not what othere think they might want.

I've seen you say that you want a stick, but you make several pursuasive arguments for a manual (your original post is confusing both ways). Think about what it takes to make YOU happy and buy it. Fuck everybody else.

Pardon me for being crude ...

If you are gonna ask, and follow the advise you asked for, blow off the Z and get a 330 convertible -- your choice, manual, automatic, or SMG. (I'd get the manual, but that's me.) Having said that, I'd really like to drive an SMG, anybody near San Diego that wants me to drive their car?

You are wrong. But then, you've never seen the insides of a US GMC auto circa 1980. They were designed to last around 100K miles, and it was rare to get more than that from them.

OTOH, Ford's C6 truck tranny would last 300-400K miles. Don't forget BMW's fiasco with GMC trannies in the late '80s and early '90s for US spec cars.

Don't forget that loss of synchro isn't catastrophic, whereas bearing/bushing failure of the planetary gear(s) is.

FloydR

Am I? It's a generalization based on my experience of many different types.

Thankfully not, but there will always be an exception.

But what failed? I was specifically referring to the gear train rather than the various clutches.

Bearing/bush failure is common on many synchro boxes too if you want to take that road. And failure of synchro cones will invariably lead on to other failures if not repaired.

But the numbers in real-life of TCs and friction clutches among different power levels of engines doesn't seem to bear that out.

Why would it make any difference whether there was a planetary gear set or a mainshaft/layshaft gear arrangement behind the clutch?

Gear life depends on accurate meshing - so the loads on the teeth are correct. Much easier to achieve in a planetary setup. On a synchromesh box there is a fair distance between bearings.