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Throw out bearing always makes contact?
In some applications the throw out bearing always makes constant contact with the clutch fingers?
The application I’m building for my Superformance Cobra consists of a 351W based stroker with QuickTime bell housing, TKO600 trans and a slave cylinder that pushes the clutch fork forward to depress the clutch, as the clutch fork end mounts to a pivot point on the passenger side of the bell housing. I noticed that the slave cylinder inner spring always wants to push the internal piston forward and that when doing the initial install I have to overcome this spring resistance which pushes the piston back down into the slave cylinder. I’m pushing the piston back down into the slave about 2 inched or so and then locking the activation rod (coming out of the slave cylinder) against the clutch fork. This puts a small degree of pressure on the throw out bearing pushing it up against the clutch face or fingers which I suspect will keep the throw out bearing constantly engaged. Is this typical for slave cylinder installations? I thought the throw out bearing was supposed to maintain a clearance away from the spinning clutch when in gear and between shifts? Perhaps this only applies to clutch pedal mechanical linkage hook ups? Thanks in advance for any thoughts or advice on this. |
Weird, this the like the third thread on throw bearing "to spring or not to spring" in the last month.
Maybe it's a springtime thing? Short answer, YES, spring on it. Why is this a complicated issue? Clutchs have been done this way for a 100 years. The throw out bearing must NOT ride on the pressure plate. I challenge ANYONE and that INCLUDES Ford tech pages, advice or quotes from Ford trained mechanics or anyone else who say's otherwise. It's BS that "modern" throw out bearings are "designed" to run with zero clearance to the pressure plate fingers. On some Mustangs with cable actuation it is virtually impossible for the auto adjusted clutch pedal to leave you with ANY clearance to the pressure plate. IF you follow Fords auto adjustment procedure your throw out bearing WILL turn constantly. Ford knows this, their answer is: It's supposed to be that way. Again, BS, thats the easy answer to avoid a serious design flaw Ford has no intention of fixing. |
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No problem, it should last about 120K miles. Bearings are funny, look at the wheel bearings, they are under constant load also. You do not have a problem and yes ford indicates it is normal because it is. Every standard transmission I ever had the throwout bearing made constant contact never had one fail in 250K plus miles.
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Thank you Maddmax, I really appreciate it. I figured a clutch fork return spring was not the answer as my set up and other similar setups I've looked at don't have them.
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Classic miss conception, Max offers nothing to back up his claims. "Testimonials" without data points are for fools.
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It's fine.
Install it that way and don't worry about it. |
My throwout bearing rides on the presure plate all of the time. The Ford dealer said that thats the way it has been for a long time. They also said that the throwout bearing should have 7 to 10 LBS of pressure on the pressure plate in the relaxed state. Being old school, I don't like it but that is what they told me.
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tcrist, they lie! :) It is difficult, but not impossible, with a Ford to establish the needed clearance. So that is the standard "line" you get from Ford (approved by the lawyers and bean counters, they didn't ask the engineers). Ram and Mcloed specifiy 0.100 to 0.300 clearance from the pressure plate fingers. How many SPF's typically come with a stock Ford flywheel, clutch disc, pressure plate and throw out bearing assembly?
Perhaps the author of this thread should be asking the manufacturer of his clutch components what they recommend? |
I believe Excaliber is correct. I am facing the very same issue. Form my research it seems there are two types of throw out bearings, one is designed to spin all the time the other is not. I would leave some clearence, just enough so the bearing is not spinning all the time.
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There are only about 100 zillion mustangs in the world that have gone their whole life like this with no problems.
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those mustangs use cables and most are in the 230-260 hp range, that is apples and oranges. It depends on the clutch, what does the clutch manfacturer recommend?
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I wonder how many millions of those 'Stangs are running an after market clutch and a near 500 horse motor, like a typical SPF might run? :)
...not many. Here's a video of one guy who bolted a strong magnet to his bell housing to attract the clutch fork and get the bearing off the pressure plate fingers. A return spring would work just as well, but the magnet is pretty trick. :) http://www.streetfire.net/video/clut...net_210912.htm |
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Seriously though, I talked to a Ford mechanic. Not the service rep, parts guy or the salesman. As I said before, I am old school and I dont like it. But with a cable clutch, what am I to do. It only pulls so far. I was thinking avout designing some sort of bell crank system that would change the throw. I am not going to change the pedal to make the throw longer. There is not much room below the pedal as it is now. |
If it really bothers you, simply remove the spring inside of the slave cylinder and install with a threaded rod and lock nuts.
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also anyone have the napa # for a new slave?? |
Personally I prefer to leave the spring inside the slave cylinder myself. Then install a clutch fork return spring to withdraw the slave cylinder piston all the way back in it's bore. THEN adjust as required. When it's right, you will have 1/2 inch, more or less, of play at the top of the stroke of the brake pedal.
Some cable type systems can be adjusted, some can't. By the way, there is plenty of evidence that those "millions of Mustangs" with zero clearance have had a BUNCH of throw out bearings replaced. Rumor has it right now, the current throw out bearings from Ford maybe defective because there are a high number of recent failures. |
I'm with Ernie 100%. But, has anyone posted a compelling reason not to install a fork return spring?
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McLeod makes extreme duty throw out bearings that are made to be in constant contact.
But why would you want to? The more a bearing turns, the shorter its life gets. I always set the clutches up for a small gap. Mark Pantenburg and I talked about this particular topic this morning. His setup probably needs a return spring as he can move his fork out further than what it returns to in its free position. |
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