No Mechanical Link Between Shifter and Transmission?

It has been said that some if not all of Toyotas problems may be due to the fact that the newer ones with automatic transmissions dont have a mechanical linkage between the shifter and the transmission. How many other car makers do this (stupidity)?

It's not really a problem as long as you are a competent driver who knows how to operate a car. As long as you have the know-how to put the shifter in "Neutral" should you have a problem, you will be fine. I have yet to see one demonstrated case where the transmission in a Toyota has failed to respond to moving the shift selector to neutral

BDison said:

How many other car makers do this (stupidity)?

Click to expand...

VW, for one.

There's no mechanical connection between the brake pedal and the brakes, either!

BDison said:

How many other car makers do this (stupidity)?

Click to expand...

Whoever "said" it appears to know as little as you.

Mercedes isn't having problems, for example, with electric solenoid operated shifting.

So going to neutral does not mechanically move a hydraulic valve, it just sends a "request" to the computer to do the same??

Yes, when you move to neutral, it flips a switch, that sends a signal to the computer, computer then sends signal to solenoid in the tranny to go into neutral. The investigators are saying that where Toyotas are messing up is the computer is locking up in the last known position and staying there, ie when passing a truck, kicked down in x gear, and full throttle. Vw atleast has a fail safe where if there is a problem, the brake will over ride the gas pedal input.

Scary. Sounds like a locked up computer can leave no ability to kill power to the wheels. So flicking it in neutral may do no good.

Probably need to go back to where a mechanical ignition switch turns off power to ignition coils. That should be pretty failsafe.

Except that they're push button start... the affected models... or some of them.

Ski in NC said:

Scary. Sounds like a locked up computer can leave no ability to kill power to the wheels. So flicking it in neutral may do no good.

Probably need to go back to where a mechanical ignition switch turns off power to ignition coils. That should be pretty failsafe.

Click to expand...

Almost everything on modern cars is computer controlled. As long as the control software is well written there are very few serious problems. Since the transmission (DSG in VW TDIs) is all electronically controlled anyway a mechanical connection would be a bad idea. Why would you want a cable (or rod) going into the gearbox when all it will do is activate a switch. It's safer to have the switch where it can be kept clean and dry (in the console) rather than where it is dirty and oily (in the transmission).

In most modern cars there is no mechanical connection between the shifter and the auto transmission. There is also no mechanical connection between the accelerator pedal and the engine. It's just the way modern cars are designed. Toyota's main problem (aside from drivers) is (was) flaws in controller software that allowed engines to rev while the brake was pressed. This "bug" was fixed in most European cars 20 years ago after the Audi "unintended acceleration" scare in the 1980s.

BTW: diesel engines do not have ignition coils.

Have Fun!

Don

I know diesels don't have coils. Was referring to the gasser world.

In any safety critical control system (auto, aero, industrial) there has to be redundancy. I think the car folks got away from this. There has to be some way to stop a machine if a computer locks up. Even if unlikely.

Ski in NC said:

In any safety critical control system (auto, aero, industrial) there has to be redundancy. I think the car folks got away from this. There has to be some way to stop a machine if a computer locks up. Even if unlikely.

Click to expand...

Redundancy costs money. How much are you willing to pay for absolute safety? I'm not rying to be snotty, but this is a decision every car maker must make at some point.

As far as stopping the vehicle goes; there is always the brakes. They are hydraulic, and this is more than enough to stop most cars. Typical auto brakes can generate upwards of 600 horsepower. This will easily overpower almost any engine in a production car. You might have to stand on the brake pedal, but it will stop the car and stall the engine. Design is always full of compromises such as safety vs. cost or reliability vs. cost, or even safety vs. reliability. The more complex a system is - the more things there are that can fail. Life is full of trade-offs.

Have Fun!

Don

JSWTDI09 said:

Redundancy costs money. How much are you willing to pay for absolute safety?

Click to expand...

[off topic] Yeah, just ask BP!!! [/off topic]

Ive always been a proponent for all essential systems to be at the very least, mechanically backed up. I wouldn't trust a car with no mechanical linkage between the steering wheel and rack, or brake pedal and brakes, and as toyota proves, i'm a bit wary of DBW throttle (and x-mission) as well.

Steel,
Please list all the cars of which you know that use a mechanical system between the brake pedal and the brakes.

1:_____________






still waiting.......

FMVSS requires a mechanical linkage between inside door handle and door latch. It also requires the inside front handle to unlock a locked latch just by pulling it (you have to pull it twice though). This is done to some guarantee of safety.

Any reasonable (and even a few less than sane) persons would expect that a requirement for a mechanical linkage between brake, steering, and wheels, be part of the standard as long as we drive the cars.

Lug Nut, a hydraulic system is considered to be a type of mechanical system. Every motor vehicle has a brake system in which at least some braking capability can be applied without relying on the power brake booster and without relying on computers and software. Furthermore, hydraulic brakes in cars are required to have redundant circuits. In cars, you have a split master cylinder with one circuit acting on two wheels and the other circuit acting on the other two. The circuits are monitored to detect failures with either circuit. In the industrial automation world, this sort of thing is referred to as "control reliability", and every safety-critical circuit needs to be assessed regarding the need for this, based on a risk assessment.

Furthermore, in most cars, there is indeed a totally mechanical braking system: the hand brake / parking brake. (I don't like the trend towards having this actuated electrically by a push button.)

It is also a FMVSS requirement that the steering linkage be mechanically connected. It can be power-assisted ... but if the assist fails, it has to be possible to operate the steering manually.

Lug_Nut said:

Please list all the cars of which you know that use a mechanical system between the brake pedal and the brakes.

1: Ford Model A

Click to expand...

there ya go.

Lug_Nut said:

Steel,
Please list all the cars of which you know that use a mechanical system between the brake pedal and the brakes.

1:_____________
still waiting.......

Click to expand...

Hmmm?

Hydraulic brakes have a direct connection through the master cylinder.OK, so there is a power assist diaphram (used to be vacuum operated, not sure what's common today), but it is still a mechanical connection, isn't it?

Parking brake is a mechanical connection through a cable direct to the slave cylinders, which serves as a rather weak alternative back up system.