Automatic Gearboxes

Out of idle curiosity, what would happen if you put an autobox into "Park" while hooning along at 80mph? Would it lock up or is there an inhibitor?

Reply to
Knight Of The Road
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I doubt you would find a box that will let you do it they normally have lockouts. Not that it would be safe to do 80mph in the UK as that is tantamount to shooting kids in the classroom.

Reply to
Depresion

Knight Of The Road ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

I'm sure some autoboxes do have, but the majority won't.

Reply to
Adrian

On a car, presuming the electromagics or mechanical lock-out mechanisms (if there are any) will let you, you'll probably break something inside the gearbox before it locks the wheels.

I've had automatic cars, but trying to engage park at any speed is not something I ever tried.

Reply to
Douglas Payne

From a safety perspective, the worst you'd do is lock up the driving wheels. I've had this happen in a FWD manual when 3rd and 5th got selected simultaneously, and I was lucky there were no corners before the car skidded to a stop on its own accord (no steering available, of course). On a RWD, the fishtailing would be very difficult to control, if not impossible.

I don't know how park locks are implemented on autos, but I imagine it wouldn't engage at speed - simply because some pin wouldn't be able to enter a rapidly moving hole.

BTW, 5th got engaged because its roller bearing disintegrated and locked the gear during a normal change from 4th to 3rd. Internal gearbox damage was extensive.

John

Reply to
John Henderson

Park is just a very crude pawl and coarse gear. There is no inhibitor, it is a very simple mechanical system. All that happens is that it makes an unpleasant noise till the vehicle stops, then it will engage. The mechanism is only a hook that drops into a toothed gear, so if the gear is spinning it keeps the pawl out of engagement. Obviously there would be a certain amount of wear of the pawl and gear, but it won't engage and even if it could it would just snap off the pawl or damage the gear.

What about engaging reverse?

Mrcheerful

Reply to
MrCheerful

Some dreadful program on Sky one (worse than 5th gear crossed with Drivel) gave it a go and couldn't get an old (rover?) auto to go into Park or Reverse when travelling forwards.

Reply to
Depresion

In news:LY-dnc4k5_5_cu snipped-for-privacy@bt.com, Knight Of The Road wittered on forthwith;

It'll go ztztztztztztztztztztztztzt-clackclackclackclackclackWhooooooooooooshhhhhhhZTZTZTZTZTTZTZTZTTZTZTwuhwuhwuhwuhwuhwuhwoooooooooo.

and stop working.

More fun is putting one of those old GM auto boxes into reverse at 60.

sometimes they still work after that as well. Built strong they are.

Reply to
Pete M

The message from John Henderson contains these words:

Quite so. Often it's a simple as the edges of the ratchet are chamfered so the pawl can't engage until it's going slow enough to find the gap, any faster and it's kicked up out of the way by successive teeth.

Reply to
Guy King

I've managed it deliberately on a Cavalier.

Reply to
Duncan Wood

One of my old college lecturers witnessed the results of a woman doing that. She went to pull into a motorway services, but the brakes failed, so as you do, she rammed the gearbox into park. Apparently, it took them quite a while to gather up the remains of the gearbox.

Reply to
moray

"Pete M" wrote in message news:f4v1hp$shv$ snipped-for-privacy@registered.motzarella.org...

Of all the auto boxes I have ever owned, all have needed you to be fully depressing the brake pedal before engaging / moving into any other gear. So I suppose to do it would require you to firstly braking extremly hard or skidding. Even then I know on my current car certain gears cant be selected if you are doing a certain speed / rpm. I tried it :)

Reply to
Matt

that is usual only on more modern boxes and then only to move out of park

Reply to
MrCheerful

Only ever seen anything similar on a MK2 Mondeo box, and then only to move out of Park.

How did you select individual gears whilst on the move, ie. 1st to 2nd, 2nd to 3rd etc.?

Reply to
<me

The message from "Matt" contains these words:

Oh, /modern/ ones. I've only owned one like that. All the others have let you play at will. And even the new ones don't stop you moving between gears - that'd be silly. How could you engage low at the top of a hill otherwise - you'd have to stop first and that'd be potty.

Reply to
Guy King

Depresion formulated on Friday :

Mine doesn't seem to have - I tried to go from 3 to D and my hand slipped pushing it further than intended into P. It made a brief grating noise as I rapidly moved it back to D, though it didn't engage the P dogs. Probably the shaft was turning too fast to let the dogs locate.

Reply to
Harry Bloomfield

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Knight Of The Road" saying something like:

I did it accidentally on an XJ12, not at 80mph but just above walking speed. Poor old park pawl was never the same again.

In short, I'd think a lot of boxes might let you do it, but it's not going to lock the box up and throw you off the road.

Reply to
Grimly Curmudgeon

Most modern boxes have an inhibitor to prevent this - as did even some early ones. Cheap and cheerful older boxes like the BW35 didn't - and all that happens is the parking pawl shears off. It's a pretty easy job to replace, too. If you shove it into reverse, either the wheels lock or a drive shaft breaks. The box survives.

Reply to
Dave Plowman (News)

I hope your lecturer didn't tell porkies too at his classes...

Reply to
Dave Plowman (News)

He was one of the good lecturers, and at the time of that incident (I'd guess 70s/80s, so there wouldn't be any interlocks fitted), was working for the same company I am now. And given the company history, common sense was not (and still isn't!) something required to get a company vehicle. We just have to pick up the pieces, and fix the motors, and not ask too many questions.

Reply to
moray

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