Drive By Wire

There is no such thing as fail-safe brakes or any other component. If you expect that level of performance from any braking system you better start walking.

That's how EVERY car felt back in the mid seventies when the first round of serious emissions controls was put on engines.

I agree. There will be *different* risks but overall I don't think it will be greater. As it is, mechanical failure as a cause of accidents is VERY low on the list of causes. And probably most of the ones that are chalked up as mech failure are really cockpit error.

A simpler solution would be to have the main brakes fail to "released" and have a better/upgraded emergency brake system that can actually stop the car in a controlled manner, unlike the ridiculous hand-operated parking brakes found on most cars these days. And it should be applied, for example, by the main brake pedal if it is pushed past a detent that can only be passed when the main brake system doesn't work.

There are many ways to skin this cat, but the best ways are significantly costlier (and not much better in any other way) than a regular old hydraulic system.

As I see it, the electrical systems in automobiles are already overcomplicated. Although not, perhaps, a big cause of failure, when something does go wrong it can be very difficult and expensive to get it fixed.

I have known people who traded cars to get away from an electrical fault that no one had been able to find and repair.

In the Consumer Reports automobile edition, a lot of cars get good marks in almost everything BUT the electrical system.

I think that this is technology that is really not needed.

Smaller and lighter internal parts do not necessarily make a more efficient transmission. How are you evaluating efficiency in this case?

Not necessarily, but the biggest losses in automatics are from the disengaged clutch packs stirring around in their fluid bath, shearing the fluid and generating heat. The smaller you make those clutch packs, the lower the associated losses. Same for the planetary gearsets- the bigger they are, the more they whip the fluid and the greater the parasitic drag. you can do other things too, like increase the disengaged clearances, but you can only take that so far. And of course computerizing the shift timing and rates goes a long way, but you still have to try to reduce the basic hydro-mechanical losses too. An automatic transmission is one of those cases where smaller is almost always less lossy. Even back in the old days, a 904 had substantially less internal loss than a 727, and those two were virtually identical in design. The 904 was simply built smaller. Smaller clutch plates, smaller gears. Same exact layout, and the controlling valve bodies were actually interchangeable.

During the middle 1970's, my father put a Chrysler-Nissan straight-six diesel engine in a Chrysler station wagon -- After a while, he wrung the driveshaft inside a 727 tranny...

Pete

I don't see how. That little diesel put out less torque than a Slant-6. Got damn good mileage, though.

Heat and loss are pretty nearly synonymous in this sort of application. That also backs up the claim that high line pressures and fast positive activation of clutch packs helps prevent losses and wear. Little old ladies dont particularly like the shift, however.

IIRC, the clutch packs, drums, etc are higher in the transmission, not turning in a bath of transmission oil in the sump. You are correct that they are wetted, but it is not a clothes washer agitator relationship.

The torque convertor has to be a main player in this heating and loss.

Line pressure doesn't have to stay high all the time. One of the criticisms of the 41TE, 42LE, and their derivative electronic automatics is that they did away with throttle modulated line pressure, which the

904,727, and the fully hydraulic FWD Chrysler transmissions had. True, they don't need line pressure to vary with throttle position since all the shift dynamics are under computer control, BUT constant high line pressure is an unnecessary load on the pump at idle (or any throttle position short of wide-open for that matter) and an unnecessary source of loss (heat). Its often been argued that the constant high line pressure may be the biggest single parasitic loss in those transmissions. Certainly the most unnecessary waste.

Well, they may not be submerged, but they DO have fluid being pumped through them all the time the engine is running. So in effect, it is just about a clothes washer situation in practice.

Which is of course why electronic transmissions lock the TC whenever possible.

I saw it the wrung driveshaft in the tranny shop -- Impressive, and the mechanic said he had never seen that before in the 727.

The problem was that the transmission was shifting too hard -- At the time he was doing the mod, an NYC taxi company was doing the same thing -- They were also having troubles and had a different modulator valve made for the 727 -- He got one and never had another problem.

He was getting about 26 mph highway with that full-sized station wagon.

BTW, the cab company found an unexpected dividend -- They were experiencing a lot less front end damage -- The driver's couldn't do their usual jack-rabbit starts! They also found that ordering cabs without 318 engines cost more than getting them with the engines, so they swapped the new 318s for mechanic work to change to the diesels.

Pete

Um.... the 727 doesn't HAVE a modulator valve. It has a throttle position pressure valve, which is why it was much easier to put a diesel engine in front of a 727 (or 904, for that matter) than something like a GM TH350, TH400, or Ford C4 or C6. All those transmissions had vacuum modulators, and since a diesel produces no vacuum they would bang into gear full-force if hooked up to a diesel.

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____________________ Thank you very much, fly. I feel exactly the same and that is why I recommend the following:

Find a better-than-average condition "older" generation model of a car you'd like to drive and would treasure for years to come - and buy it!

For example, I'm in the market right now for the LAST generation of VW Jetta, the ones from 1999-2004. They had good ole' fashioned HYDRAULIC-assist power steering, none of that electrical CRAP, and much better than average handling ratings than did other compacts(Japanese/American/etc.) from that period.

-CC