QuestionQUESTION: I have a 1974 MGB and I have replaced the clutch master and slave cylinders. I have bled the lines and no air is present but it is still hard to shift. The clutch pedal is firm and I have to push all the way to the floor to shift. Works fine sometimes but more often than not it is hard to shift as if the pressure plate is not releasing. thanks
ANSWER: Hi Wayne,
If the free play is not excessive in the pedal and the pedal feels firm as soon as the free play is taken up and the clutch will not release completely then the problem is most likely inside.
But first you need to go into more detail as what you are calling hard to shift. Hard to move the lever, shifts but grinds, hard to go into gear but no grinding, hard to get out of gear but no noise, or what?
The test is to have the engine warmed up and at idle (below 1000 RPM) for at least 10 seconds with the clutch pedal on the floor and in neutral. Then push it into 1st gear quickly. Did it crunch or make the car move at all? Then put it back into 2nd gear and still at idle and push it into neutral. Did it go smoothly?
Many things can make it not shift correctly. The clutch can drag because the hydraulic system did not retract the pressure plate, the pressure plate may not release straight and one corner can drag. The disk itself can cause a drag by being warped so the pressure plate can't retract far enough to completely release it. The disk can bind on the shaft and not release away from the flywheel even though the pressure plate did retract far enough. The pilot bearing can drag the input shaft (1st motion shaft) and act like a dragging clutch. The syncros in the gearbox could be worn out making it grind each time you shift.
Many mechanics require that all the clutch components be replaced for this reason. Most shops will not put any component in the clutch system without all the parts being replaced.
Even the hydraulic system is the same, never build a master cylinder without doing the slave too.
Howard
---------- FOLLOW-UP ----------
QUESTION: Thanks for the fast response. You asked for more information Item one: I have very little free play, maybe an inch or less and the pedal feels firm after that.
item two: It was hard to shift into first gear and all other gears were smooth after I got to speed. There was no grinding except sometimes going to reverse.
item three: I tried your test of waiting for 10 seconds and going to first and then to second. This method was smooth and easy. If I tried this with the RPM above 1000 and not waiting, I had trouble getting into first gear. I tried it again after waiting a few seconds and low RPM and the shift was smooth to all gears. Maybe my shift problem is ME.
Thanks again.
Wayne
AnswerGood answer Wayne. I didn't want to say that but you can say it.
The reason for the wait is that the design of the system is that when the clutch pedal is up, the disk, input shaft and ALL of the gears are spinning at engine speed even if the gear box is in neutral. When you push the pedal to the floor you release the disk. But since it was spinning at engine speed and it has a lot of mass, it wants to keep spinning even though it has been released from the engine (thus the 10 second wait) (5 seconds in the winter because the gearbox oil is thick)
The higher RPM just means the disk and all the gears and the input shaft take much longer to coast down to a point that the synchronizers in the gearbox can get it into gear.
You should read my tech tip on how to make a straight stick gearbox last longer. (a lost art today) http://mg-tri-jag.net/tech4.htm
Glad you were able to fix the problem.
Howard
