Wheel spin in neutral, is this normal? Options

[rwilner]

My car is on 4 stands right now. When I start it up in neutral, the passenger side wheel slowly rotates clockwise while the car is idling (as if the car were moving forward). I can easily stop it with minimal force using my hands. I have not checked to see if the wheel will stop rotating once I push the clutch in, as my wife is at work and the cats aren't interested in helping.

Is this normal? if not, what does it mean -- my clutch cable is too tight?

[AndyB]

My car is on 4 stands right now. When I start it up in neutral, the passenger side wheel slowly rotates clockwise while the car is idling (as if the car were moving forward). I can easily stop it with minimal force using my hands. I have not checked to see if the wheel will stop rotating once I push the clutch in, as my wife is at work and the cats aren't interested in helping.

Is this normal? if not, what does it mean -- my clutch cable is too tight?

Yeah its normal my cats don't like helping either (IMG:style_emoticons/default/biggrin.gif)

[Valy]

My car is on 4 stands right now. When I start it up in neutral, the passenger side wheel slowly rotates clockwise while the car is idling (as if the car were moving forward). I can easily stop it with minimal force using my hands. I have not checked to see if the wheel will stop rotating once I push the clutch in, as my wife is at work and the cats aren't interested in helping.

Is this normal? if not, what does it mean -- my clutch cable is too tight?

The spin is normal, caused by the oil spinning in the transmission.
I would check why only one wheel is spinning. Is the caliper stuck on the other one or the bearing bad? Don't worry too much but do a sanity check - see if something makes noise when you spin the wheel with your hand.

[Rand]

I would check why only one wheel is spinning.

Both wouldn't spin unless you had a welded diff or some sort of posi/limited slip, right?

[914.SBC]

That cat remark was funny.

[SirAndy]

I would check why only one wheel is spinning.

Both wouldn't spin unless you had a welded diff or some sort of posi/limited slip, right?

I'm pretty sure you are right ... It's usually only one of the wheels that spins ... (IMG:style_emoticons/default/shades.gif)

[nathansnathan]

if you hold the 1 from turning, the other should start turning in its place.

[stugray]

The spin is normal, caused by the oil spinning in the transmission

How is it possible for anything in the tranny to be moving (oil or mechanical), if the clutch is not engaged?

It's not like the tranny is a magical device that can do work without the engine turning it....

It sounds to me like your clutch is dragging.


Edit - just re-read the post. If you are in neutral, then parts in the tranny ARE turning.
It should NOT do that with the clutch depressed.

Stu

[flipb]

The spin is normal, caused by the oil spinning in the transmission

How is it possible for anything in the tranny to be moving (oil or mechanical), if the clutch is not engaged?

It's not like the tranny is a magical device that can do work without the engine turning it....

It sounds to me like your clutch is dragging.


Edit - just re-read the post. If you are in neutral, then parts in the tranny ARE turning.
It should NOT do that with the clutch depressed.

Stu

The clutch is engaged. Transmission is in neutral. Input shaft (or something equally technical-sounding) spins in neutral.

Edit: You made an edit while I was replying. Now back to your regularly scheduled programming.

[nathansnathan]

In the pelican parts "how to adjust your valves' article they make use of this feature to make it so you don't have to keep getting out from under the car. They say to roll up on 1 ramp only and then jack up the other side, so you'v'e got room to work under there and then the 1 wheel is held stationary.

I guess it's a little different since you're in neutral and to do this all you have to be in a gear, but if you turn the free wheel from under the car (that's the point, to be able to stay under the car), you're then turning the engine. If you think the one wheel spinning is weird, what happens if the other wheel isn't held stationary is even weirder, as it will spin in the opposite direction! I've always thought that was just crazy.

Honestly that seems like a retarded way to adjust your valves, as you'd have to drive off after the first side, and set it up the other side to do the other.

I guess I've never had the pleasure of adjusting valves in a 914 though, as I've never actually driven mine. (IMG:style_emoticons/default/smile.gif)

[Valy]

I would check why only one wheel is spinning.

Both wouldn't spin unless you had a welded diff or some sort of posi/limited slip, right?

I'm pretty sure you are right ... It's usually only one of the wheels that spins ... (IMG:style_emoticons/default/shades.gif)

In ideal conditions both wheels will spin. If one of the wheels is blocked, even a little since there is not too much power involved there anyway, the differential will compensate for that by spinning the other wheel twice as fast.

You need to understand that when the internal friction of the differential is less than the wheel friction force, the differential will spin and turn the other wheel. Once the other wheel turns, its friction coefficient changes to a lower one and it is easier to spin it so it will continue to spin even if the other wheel friction is reduced a bit.

Anyway, if only, one wheel spins, just check the other. It may be just a bit a dirt somewhere that should not present any concern but it can also be a bad bearing or a stuck caliper. As simple as it sounds.

[r_towle]

Simplest way I have found to adjust my valves (every 3-5k miles btw) is on my back, spinning one wheel in 5th gear.

On the why does it spin in neutral, I dont buy the oil answer.
I would think (and I dont know) that the input shaft does spin because its connected to the flywheel and there is some friction there.

It also happens due to momentum...once it gets going it goes faster and faster, so I think it is directly related to the input shaft, the input bearing and the limited amount of friction that is in that coupling.

When you are in neutral, the input shaft spins and it is so close to the output shaft , pinion shaft) that it could get it going lightly.

If you grab the wheel, it does stop.
Never tried to stop both sides though..I will next time to see what happens.

Rich

[zymurgist]

My 911 does that when it's running and on jackstands (yes, contrary to popular belief, 911s need to be worked on too (IMG:style_emoticons/default/wink.gif) ), and so does my motorcycle when it's running in neutral on the center stand.

[Richard Casto]

I think Rich got his answer, but as to "why" this happens...

The input shaft in the transmission is turning (as already stated). Car is in neutral, so the input and output shafts are not locked together via one of the gears. But remember that all of the five forward gears are in constant mesh, but are freewheeling on either the input or output shaft. If you had perfect zero friction bearings, etc. the gear that is freewheeling would not transmit any power. But real world friction allows some power to be transmitted from the input to output shafts. Then it is just a matter of overcoming the friction of the differential bearings, one or both of the wheel bearings, brake pads, etc. If all of that is overcome, then you will get a wheel to turn.

The best way to see this is to take a gear stack that is out of a transmission, make sure it's in neutral and then spin the input shaft. You will get the output shaft to spin as well. Of course the power being transmitted is minimal.

Richard

[maf914]

Now, if you had really slippery oil in the tranny, none of this would happen. But it would have to be really, really slippery... (IMG:style_emoticons/default/laugh.gif)