Opinions on placing car in neutral at stop lights. Options

[Cuda911]

Some people claim that if you are a a stop light with the car in gear, but clutch pushed all the way in, that it wears out the throwout bearing faster.

I had a lengthy discussion about this with one of our 914World member and a 914 guru of the highest Grand Master level (Mugsy). He convinced me that it is fine to idle at a stop light with the car in gear and clutch pushed in. So, that's what I usually do. Every once in awhile it's tough to get the car in 1st, and I don't want some F150 riding over me when the light turns green and I'm on an easter egg gear hunt.

Yesterday I was driving a friend's '71 911, and he started giving me crap for not putting into neutral at lights (Mugsy, you guys got the motor sounding great!).

Just thought it would be interesting to solicit the group and see what your thoughts are on this topic.

[screenguy914]

My humble comments related to the discussion:

"Even with the tranny in neutral and the clutch engaged, the internal parts are spinning. This is evident if you ever jack up the rear of a car with the engine running.

Even if the clutch is disengaged, there is enough drag and kinetic motion to keep parts spinning."

The above description means the clutch isn't fully disengaged, even with the clutch pedal floored. There should be no drag or kinetic motion in a vehicle at rest and the transmission disengaged from the drive train. Adjust the free play to properly disengage the clutch mechanism.

"The 914 and 411 manuals didn’t really talk about these issues,………"

That's because the owner and repair manuals aren't basic automotive reference manuals. Most basic automotive books don't even address this unless there's an intermediate/advanced section on drivetrain diagnosis and repair.

However, many posters are correct in their responses. Under the specified conditions: - the TO bearing rotates
- the pressure plate fingers are compressed
- the force of the pressure plate springs are transferred to the flywheel and crank which increases axial load/wear on the thrust surfaces of the crankshaft main bearings.

"No merit whatsoever. Since sometime in the 80s all manual trans cars have a kill switch to prevent one from starting the car without having the clutch released." (referring to crank thrust bearing wear)

The last year of the 914 was 1976. Most cars before then did not have a clutch override switch. The above doesn't apply

"I coast down until the engine is @ idle speed and put in neutral without using the clutch.
At idle speed there is no resistance."

When in gear, the input shaft rotates, clutch engaged or disengaged, vehicle at rest or moving. If you wait until the vehicle stops before shifting out of gear, the still engaged drivetrain should cause the engine to stall (all still connected via the clutch). If you move the lever out of gear w/o the clutch, you're separating parts still under a slight load. Some wear - could be insignificant or not.

To the original poster, Cuda911. It's not automotive heresy to leave the clutch disengaged at idle, but some wear is caused by this strategy. Difficult shifting into 1st is a common occurrence with early, post 901/915 gearboxes. Sometimes,it's a function of adjusting the proper clutch pedal free play. It's also an expedient short cut owners discover to get into gear when a normal shift from neutral>first is balky. It's a common symptom of worn synchros, especially in 1st and 2nd gears. We can save the whys and solutions for another discussion.

[Mike Bellis]

My humble comments related to the discussion:

"Even with the tranny in neutral and the clutch engaged, the internal parts are spinning. This is evident if you ever jack up the rear of a car with the engine running.

Even if the clutch is disengaged, there is enough drag and kinetic motion to keep parts spinning."

The above description means the clutch isn't fully disengaged, even with the clutch pedal floored. There should be no drag or kinetic motion in a vehicle at rest and the transmission disengaged from the drive train. Adjust the free play to properly disengage the clutch mechanism.

While your theory is valid, here are some things to consider.

With the clutch pressed in, the throwout bearing is under pressure. The pressure plate and flywheel is spinning. the disc slides on the shaft and may make contact with either surface, thus spinning the disc and the main shaft. For your theory to work, the disc would need to self center between the pressure plate and flywheel. While it may do this at times, odds of it happening every time is slim.

If the car is stopped, the disc will slip inside the open area between the pressure plate and flywheel and the car will not move as long as the clutch pedal is pressed. The space created is not much wider than the disc itself.

I would challenge you to jacking your car up and test the theory and prove nothing but the flywheel and pressure plate are spinning.