Crank Walk with a Manual Transmission

Rather than use a thread started by jplaxco2, this seems better to take the topic of crank walk, or crankwalk, to a side bar.

Crank walk is apparently a thing; but, I have a hard time believing it is caused by holding the clutch pedal down for extended periods like while waiting for a traffic light to change.

Some bullet comments:

1. If true, then each gear change places wear on the crankshaft thrust bearing.

2. Looking at the simple diagram below, the flywheel/crankshaft should have no pressure with the clutch pedal pressed.

3. If comment #2 is true, then the inverse is that there is constant thrust on the crankshaft while driving.

 

It's actually the inverse of what you said. There is no thrust pressure when the clutch pedal is released. When the pedal is pressed, it pushes the clutch fork into the throw out bearing. Thus putting pressure on the fingers of the pressure plate. That forward pressure is transferred into the flywheel and the crankshaft.

EDIT: Mitsubishi had a bad problem with that on the early 2nd Gen Eclipse Turbo's. It was made worse when a heavy duty aftermarket pressure plate was installed

 

1. Is true, but a gear change only takes a second and the oil on the thrust bearing further insulates the bearing from wear. The amount of wear from a shift change is negligible. My brother has 430,000 miles on his first gen and is still on the original clutch.

2&3. You have it backwards. Referring to your diagram: When you press in the clutch the release bearing pushes against a set of spring loaded levers in the center of the cover plate which lifts the pressure plate disc off the clutch disc effectively disconnecting the engine from the trans. Meanwhile it is pressing against the cover plate which is bolted directly to the flywheel which is bolted to the crank which is then pushed forward against the thrust bearing. This is a somewhat simplified explanation for clarity's sake.


That being said, there is no way the other guy wore out the thrust bearing in 38,000 miles no matter how much stop and go driving he did.

 

Sure looks like the "forward pressure" is applied to the engine block, no?

 

Unless you had a manufacturing/servicing defect, crankwalk is more common with automatic trucks that tow or occasionally manual vehicles with an extremely stiff pressure plate. Reason being the torque converter overheats, balloons out and in turn puts excess pressure on the thrust or the increased pressure to disengage a clutch with a stiff pressure plate will do the same

 

Ok, didn't realize the clutch cover and pressure plate were bolted to the flywheel. Thanks.

 

I have seen plenty of thrust bearing failures on early Toyota 4cyl and v6s. Almost always came in as a complaint of belt noise that coincides with stepping on the clutch. Some on the cranks would move 1/2”, but run great otherwise.

 

Yeah, there's a moveable pressure plate inside the cover plate which clamps the clutch disc against the flywheel when the clutch is out.

 

Useful comments guys, thanks. Still in disbelief that crank walk was the explanation used by that Toyota tech in jplaxco2's situation.