Automatic transmission question

[Selectron]

A car with an automatic transmission will normally have a safety switch, which will prevent the starter from cranking the engine unless the transmission is in Park or Neutral. Now just suppose that switch developed an internal short-circuit fault - it would then be perfectly possible to crank and start the engine whilst the gear selector was set to one of the Drive positions - what would be the implications of doing that?

Would the engine simply stall, or would the car lurch forward, or would it actually start driving forwards, or would the transmission be damaged, or what? (I'm in the UK and almost all cars over here are manuals, so I don't know much about automatics).

[curtis73]

It would start, and provided your foot was on the brake it would just idle in gear. Most transmissions would wait a second to drop in to gear since it takes hydraulic pressure to engage.

I had a I/O boat that was stuck in forward. I would start it and it would start moving. Things would be very similar in a car.

However, for safety reasons, all neutral safety switches are designed so that if they fail you can't start the car at all.

[Selectron]

Thanks, that pretty much covers what I wanted to know. I've been driving since the mid-'70s and I've driven an automatic just once, for a distance of only a few miles. There will be many drivers here who've never driven one at all.

[SLJ2137694]

I have personally had Neutral Start Switches that were mis-adjusted that allow the engine to start with the transmission in gear. This could cause the vehicle to lurch forward or backward when the engine started if your foot was not on the brake.

[J-Ri]

They'll move alright... offroaders with manual transmissions will bypass the switch so if they stall going uphill, they can use the starter motor to get them moving and they don't lose traction from rolling backward. I once saw a guy put a car THROUGH a wall because of a bad switch.