Engine a dumb question

Because of the design of the differential. You'd have to have an understanding of how the differential works (www.howstuffworks.com has a really good explanation of it). Basically, when in park the wheels will not rotate in the SAME direction, but the differential design allows them to rotate in opposite directions.

Now - if both front tires are firmly planted on the ground and the vehicle will roll in park, then you definitely have a problem. But if both are off the ground - it's normal for them to rotate in opposite directions.

You might also notice that if the front wheels are off the ground and you start the engine, put it in gear and let both wheels start rotating. Assuming it's just idling, you can grab ahold of one wheel and stop it, the other wheel will start spinning twice as fast. That's why open differentials (read: most stock diffs) suck - they transfer power to the wheel with the LEAST traction. An that doesn't get you anywhere fast.

Trav

a dumb question

I've always wondered, why on fwd vehicles do the front wheels spin when the car is in park? I had a car on a lift today in class and it just stumped me.

No, when it is in park, it should lock the wheels in place.. for example, put an auto car in neutral and try to push (like a corolla), not that hard to push on a flat surface... now put it in park and try that again... you won't be able too, you'll have a little bit of play (which are the gears in the tranny giving the little bit of play).

Thanks, I got it now. I just figured that out today changing tranny fluid on another car.

Lol my auto teacher doesn't know much, I had to show him how to flush coolant.

lol haha that sucks... What kinda skool/teacher is this? Man I wish I could get paid to not know stuff haha.

<br />
haha since u were in class, u coulda asked your teacher...

here's my dumb answer to your dumb question.....uh I dunno? =)

CorollaULEV,
Thanks for the discussion about differentials. That helped me.
Rep points to ya.

Yeah thanks that was pretty helpful. My auto tech teacher just has a industrial tech degree. Doesn't know much about cars. Basically I just take it cause its a lot more fun elective than sculpting or something like that.

So it would be safe to lift the car up on jackstands, put it in drive, and grab ahold of one of the wheels. I actually revved the engine in drive with the car jacked up and those wheels go fast and make lots of wind lol.

I think that could be dangerous and the engine should be able to overpower you I would think.

If the engine is off, then sure it's safe. If it's not..well, I wouldn't.

Yep, its the differenetal.

Well, it's not safe if the speedo is saying 50mph, or even 10mph, really. However, if it's just idling in 1st gear, then the wheels aren't moving very fast - like 3 or 4mph. Plus, as said, stock differential design will freely allow one wheel to stop spinning.

Trav