Park gear

[jeepien]

It occurs to me that I have no idea what the P button actually does on a Prius.

I know what happens in a conventional automatic transmission when it is shifted into Park, but that doesn't give me any point of reference here, because the power splitter is no conventional transmission.

I've read several discussions about how the planetary gears split power among the various components, and it was good reading, but none of them addressed the Park function.

Maybe [you] knows?

[efusco]

same concept. Just drops a "stopper" in the system in the PSD...it is mechanical

[Tideland Prius]

haha me? no no. There are way more knowledgeable people than me. I'm only in 2nd year university!

my best guess is that it's to simulate Park in a regular tranmission (so I guess, locking the gears?).

htmlspinner, john1701a, danman32, Frank Hudon and many others can probably give you a much better and more technical response

[ltu1542hvy]

Maybe [you] knows?

Sorry, I sure don't. I too am assuming that it mimics the function of the Park gear in a regular automatic transmission. But that is pure speculation. There are people on this board who are infinitely more knowlegable than I am about these matters, and hopefully one of the can answer.

As an aside, I'm finally picking up my Prius tomorrow. I doubt I'll be able to sleep tonight out of anticipation.

[Robert Taylor]

Hey, congrats on getting the Prius, you need to print off the delivery checklist that is on this site and use it.

Mid-week I was at the Toyota dealer's parts counter and that set of repair manuals for the Prius is avaliable through the 800 number cited in the back of the Prius owners manual. I keep thinking that this is a worthwhile investment, even though it is likely to rival a college textbook in cost.

I can tell you that I have experienced a little confusion of expecting the car to move after taking off the parking brake and not shifting it, and then I feel some loading going on like a catchpaw of a typical automatic transmission. (yeah, I was distracted by passengers, cell phone, etc. those two occasions)

Now, if a regular automatic transmission gets that catchpaw "loaded up" by holding a vehicle on steep grade or being hit by another vehicle and pushed, it puts a load on that catchpaw that is VERY hard to get out of park by moving the transmission lever.

If that ever happens in a regular vehicle, DO NOT attempt to force the transmission out of park. Get another vehicle to push you uphill, or the direction you pushed from to "unload" the catchpaw.

Personal experience? Yes, I went to a football game, parked on the steep grade of a side street, failed to set the parking brake as hard as I could and it loaded the catch paw. I forced it out of park and destroyed that transmission in short order. Obviously I smashed some metal off in that yank out of park and I WILL NEVER DO THAT AGAIN.

So, the moral of my sad expensive tale is that:

1. Treat that gear with tender loving care
2. Make a special point of setting that parking brake as good as you can on a grade. DO NOT let off the brake until you set that parking brake as hard as you can on steep grade.
3. In a Prius, their is some setup to let the mechanical catchpaw out, but it still can get the load put on it, if it acts squirrely then get another vehicle to "unload" it.

I'm not the genius, I am the guy that blew the expensive transmission. Experience is the most expensive teacher, so learn from others is cheaper.

[pepa]

Maybe [you] knows?

Nah, I have Prius for only 3000 miles, and most of what I know about the vehicle comes from others here. I'm no expert by any stretch of imagination.

My driveway is uphill, and when I press P and let go the brake pedal, something "clicks" and the vehicle backward movement stops. Just like my old '91 Camry did.

[Tempus]

It's a normal physical parking pawl. IE, it's a wedge that goes into a gear somewhere in the drive train to keep it from rotating.

It's electro-mechanical instead of purely mechanical, I'm assuming a servo of some kind.

Only place I've seen it mentioned by Toyota is in the Emergency Response Guide

http://techinfo.toyota.com/public/main/2ndprius.pdf

I'd bet it's not in the PSD. Remember, there are gears between the drive shaft and the wheels outside the Motor/PSD/ICE assembly and it seems logical that it's in there. But, it could be in the side of the PSD too.

[Canuck]

Yes.. to answer your original quest from the font of all Prius knowledge,(Canuck)... all of the above posts which correctly answer your question would have been my reply. Sorry to have been absent from being available to answer this most important question but I slipped on the ice the other day and have been busy getting stitches and a cast on my hand. I am happy to report that our humble 2005 Prius pulled herself through the most mountainous snow (3-4 feet) banks during the emergency where I was safely placed in the hands our British Columbia Health system and spent a only 6 hours to get an X-ray and a cast without spending a dime except for the $1000/year taxes.

[jayman]

emergency where I was safely placed in the hands our British Columbia Health system and spent a only 6 hours to get an X-ray and a cast without spending a dime except for the $1000/year taxes.

Hmmm, I sense a certain, how shall I put it ... hostility??

My Dad is American and my Mom is Canadian. Half their working lives in the U.S., half in Canada. They can't move back to the U.S.

Well, they can any time they want to. They'd just kiss away their OAS, CPP, etc etc. They would love to move to a climate where it stays nice year round, like southern Utah. You can bet I'd ditch this place in a heartbeat!

If anything serious happens, I drive them into Minnesota or ND. My Mom once spent 12 hours waiting for an x-ray after she slipped on some ice. Yeah, let's not forget all those high taxes they paid while working.

[jayman]

Sorry about the delay jeepien, just got back from an aborted attempt to drive out to the hobby farm. Had another nasty blizzard and they just closed the Trans Canada. Almost got stranded in BFE too.

Thank God for winter tires. It's very bad out there.

I have the shop manuals on order. Until they arrive, I can only guess the Park button uses a solenoid to engage a pawl to lock the transaxle.

Some have expressed concern about parking on steep hills without using the parking brake. This concern is valid, especially if the car is facing backward down the hill. I doubt the solenoid would be able to disengage the pawl. Usually you need a push to relieve the pressure on the pawl.

As Robert Taylor mentioned, you can cause $$$ damage if not careful. Especially on a modern electronically controlled transaxle with nothing "extra."

Most older automatic transmissions (Ford C6, Chrysler 727, Chevy TH400, etc) were very stout units. Very inefficient, but very stout. The parking pawl was a large metal finger that latched onto the splined output shaft. You really had to try hard to bugger that up.

I think it's a very good habit to set the parking brake before pressing Park. This way you don't have to worry about the parking pawl. About the only time I wouldn't recommend using the parking brake is if it could freeze.

I speak from experience: that is NO fun.