Clutch not completely disengaging

[epj3]

I know I have seen this problem on other cars before (not my own), and was curious how to fix it.

I always felt as if the clutch never completely disengaged so I took the car out on a very flat surface, and with the pedal pressed in at idle, when I put the car into first gear it lurches forward a VERY small amount. Now, I know my throwout bearing is going to be bad in a few months - but I also know my slave cylinder could be going bad. The clutch does engage fine with no slipping, but I assume that if the disc were worn down enough, the slave cylinder wouldn't be able to extend far enough to completely disengage the clutch.

Any idea's? I'll be bleeding the clutch this week sometime. If that doesn't help, I'll do the slave cylinder next month when I do the clutch (and lightweight flywheel... )

 

[jrt67ss350]

II assume that if the disc were worn down enough, the slave cylinder wouldn't be able to extend far enough to completely disengage the clutch.

Not true. If anything, a worn clutch disc will result in a more complete disengagement of the clutch since the clutch disc will be thinner due to the wear.

You sure that the car isn't momentarily moving forward when you engage first gear simply due to the transfer of inertia of the rotating gearbox parts? When you have the car idling in neutral with the clutch engaged, the input shaft and layshaft are rotating at engine speed. When you disengage the clutch, those parts are still rotating due to their stored inertia. If you rapidly shift to first, the first gear synchro has to very quickly slow the input shaft so it can mesh with the layshaft via first gear (and since the car isn't moving, the output shaft is not rotating. Therefore, the input shaft has to be completely STOPPED by the first gear synchro in order to mesh the gear without grinding). Since the car is not moving and is on level ground, some of that inertia gets transferred to the output shaft and can cause the car to move a small amount.

My '87 does this - did it with my old clutch and does it with my new clutch. My dad's '89 S-10 pickup does it too. It's just a small amount of movement, though - certainly not a lurch or jerk by any means.

Try it again, but wait 30 seconds after disengaging the clutch before shifting from neutral to first. That will give the rotating tranny parts time to stop rotating. Then, when you shift to first, there will be no rotating parts that need to be slowed before the gears can mesh. That will also give the master and slave cylinders time to "bleed down" if they aren't up to snuff and result in a more abrupt engagement if they are bad.

 

[epj3]

All good points, but if I have the clutch pressed in, put it into first, then take it out of first without removing my foot, and place it in first again, it seems to still do it.

 

[jrt67ss350]

All good points, but if I have the clutch pressed in, put it into first, then take it out of first without removing my foot, and place it in first again, it seems to still do it.

Hmmm....well that screws my whole explanation above. It would have to either be the master, slave, or pressure plate resulting in the clutch not completely disengaging.

 

[epj3]

Yea i'll have to check again though - because I DO notice it's easier to put in first if I shift down into 2nd first then into first gear...