Z4 automatic vs. stick

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Poor design or materials, then. Most autos go to their grave without suffering that sort of failure.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Since almost all GM autos from that era die with that failure, your statement that "most" live is obviously incorrect. I agree that it's poor design: a ball bearing carrier (rather than the cheaper roller bearing and thrust washer) would last much longer. Doesn't change the facts, however.
FloydR
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But I'm speaking from a UK perspective. The GM autos from that era used here tended to be the larger ones fitted to Jaguar and Rolls Royce.

Facts depend on where they're gathered from.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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When did we start speaking from a UK perspective? (I'm not going to bother to look, as I no longer care.) This is a global group, not UK specific, so "facts" should be world-wide, not cherry picked from one country.
Later.
FloydR
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Indeed. The point I perhaps was trying to make more honestly after you started talking about 'US GMC autos'. ;-)
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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No. It's a US-perspective (or even LA-perspective) NG...
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Since it *is* a US originated group I try to make it plain where I hail from.
Wish it were the case with some others writing to car groups with 'uk' in the title...
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

What makes it a "US Originated group"?
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On Thu, 23 Nov 2006 18:49:40 +0000 (GMT), "Dave Plowman (News)"

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.
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wrote:

Because the TC will handle a heck of a lot more torque application. It "gives" where the friction clutch wears out.
Eisboch
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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?
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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.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Sun, 26 Nov 2006 12:32:45 +0000 (GMT), "Dave Plowman (News)"

That's a good argument *for* putting a planetary gearbox, rather than a synchro. one, behind a friction clutch. I'd love to know what I've missed that would tell me why it's not done.
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Probably because you've already got 'clutches' in a planetary box which can do the same thing. Didn't the Model T Ford use this principle? Later pre-select boxes of course used a fluid flywheel for starting from rest.
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On Sun, 26 Nov 2006 13:18:26 +0000 (GMT), "Dave Plowman (News)"

Then why do you *have* to have a torque converter? Oh dear, I'll never understand this...
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It has several functions. First it acts as a 'clutch' when starting from rest. Next it acts rather like a continuously variable gearbox by allowing the engine speed to exceed its output speed by up to around 2000 rpm and converting most of that speed into extra torque at lower output RPM. Not all though, as it gets hot in doing so. ;-) It also - and crucial for most autos - cushions the actual gearchange.
When autos had two or three ratios, the torque multiplying feature was crucial to reasonable performance - albeit at the expense of economy. Boxes now have up to what? 8 ratios, so this part isn't much needed. So many just use it for starting off and each gearchange, locking it out of action via an extra clutch for most of the time.
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On Sun, 26 Nov 2006 16:12:36 +0000 (GMT), "Dave Plowman (News)"

I've always had a pretty good grasp of the mechanics of it all, including how the TC works and the subtleties of what it does.
I was kind of thinking that torque multiplication rather than the 'disengaging' effect of low torque transmission at low RPM was the underlying reason they were first used, and I suppose there was then no real reason to change things later.
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wrote:

A fluid flywheel is not the same as a torque converter. A TC will direct oil flow onto a fixed stator that in turn directs oil flow to a turbine attached to the gearbox input. whereas a FF is simply a spinning container of oil that inertia eventually makes the outside tank oil viscosity turn the vanes of a "spinner" connected to the output to the gearbox. David Brown tractors used to have this arrangement and a similar arrangement although not fluid was the magnetic flux flywheel (clutch less) setup designed jointly by Jeager and Smiths and fitted to the once famous Hillman Minx and I think Simca or Renault cars in France.
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Unlike a clutch, it is not possible for a torque converter to completely disengage so there would always be some torque present during shifts which would wear out the synchros in very short order. That's also the reason that a standard transmission will outlast an automatic by a factor of two or three. If you want to keep your car for more than 300k miles I would not recommend an automatic.
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wrote:

That's completely the opposite of my quandary!
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