Clutch slave cylinder, internal spring?

[wrogers55]

I know this subject has been absolutely beat to death...but.

I'm finishing up a full clutch replacement and down to the slave cylinder issue.

I have a "push" 7/8 slave with a 7/8 master. The slave has an internal return spring that pushes the plunger OUT, with something like 6 to 8 pounds pressure. That means that any clearance between the release bearing and the pressure plate fingers is "taken up" by the return spring and the bearing rides on the fingers full time. I know the Ford Mustang guys say that's no problem and the bearing is made to run on the fingers full time and the old school guys, like me, don't like the idea of the bearing running when it's not needed.

What works here? A stronger return spring to overcome the internal spring in the slave? Or, take the return spring out of the slave and use a external return spring that keep the fork arm off of the bearing fingers when disengaged? Or, leave it alone and let it run on pressure plate fingers?

By the way a factory race team Ford/Cosworth engineer told me that there is more stress placed on the bearing when it NOT in full contact with the PP fingers than when it has some clearance. Some version of the bearing going from full stop to high rpm spin up at every shift with a synchronized trans being harder on the bearing than just letting it run full time. That's not my argument, nor have I adopted it, just passing it along.

This should be easier. Thanks for the help.

[jhv48]

Install it and don't worry about the tension the spring places on the fork.

Modern T/O bearings will be fine with that small amount of pressure. Basically, it just takes up the slack in the piston.

[Excaliber]

Hmmmm, I'm still leaning "old school" on this issue. I don't like the idea of my throw out bearing touching the pressure plate unless I'm shifting.

...having had to replace a couple of throw out bearings in my time when the clutch was still perfectly good may be the reason.

I run a "return spring" on mine for that very reason, AND I keep the clutch adjusted for a little free play.

When I'm aggressively going through the gears I don't take my foot off the clutch, just let up on it, thus removing all the freeplay. PLUS the return spring does not act that fast. Not fast enough to take up the slack and provide free play between shifts up or down, on the street or the track when your playing or driving seriously.

However, on the highway, there is enough time for the spring to provide free play so the bearing isn't being spun for a miles and miles at a time.

Old school, they got it right the first time.

I bet the throw out bearing on my 427 side oiler is essentially the same materials and style of build today that it was in in the '60's.

[jwd]

I agree 100% with Excaliber. I removed the spring from the slave and added a return spring to keep the T/O bearing off the pressure plate.

In the "old school" days, if your T/O bearing constantly rode on the P/P fingers, you'd be replacing it in less than a 1000 miles. If you kept it off the P/P, they'd last 50,000 miles or more. I believe the same holds true today.

Jim

[Bernica]

I've seen this subject debated here soooo many times.

Does anybody know how to do a poll here amongst us? "Should your TOB be in contact with your PP: Yes or NO....

Just a thought to see what the masses have to say.

[Trueoo7]

How do you know if its in contact or not? Is it by sound or feel?

[Rick Parker]

It translates directly to the freeplay in the pedal. Adjust as needed.

[wrogers55]

To answer your question about constant contact, the internal spring in the slave pushes the clutch fork arm forward until it it stopped by the bearing touching the fingers of the pressure plate. You can feel no free play in the arm at that point. And, you can see it in all its glory through the window hole where the clutch fork arm comes out.

It's still a matter of "to touch or not to touch". I guess that goes for lots of things actually.