Am I correct in assuming that hydraulic clutch setups allow the throwout bearing to ride on the clutch fingers even when the clutch is engaged? With mechanical linkage we were always told to have some pedal free play to prevent contact with the TO bearing when the clutch is engaged and prevent premature failure of the TO bearing....have the rules changed for hydraulic setups? Is the TO bearing used with hydraulic setups different than mechanical linkage?
I'm using a Ram hydraulic throw out bearing. When you set it up there is clearance between the fingers & bearing when its disengaged, so its just floating on the front bearing retainer, until you push the pedal.
You could have a slave cylinder and fork mounted conventional TO bearing or an actual hydraulic throw out bearing. There's a spec clearance between fingers and bearing.
The spec for the amount of required clearance is different, but there is still clearance between the throw out bearing and the clutch fingers with a hydraulic TO bearing.
With a master cylinder, a conventional slave cylinder and a sliding TO bearing the only thing that returns the pedal is the pressure plate pushing on the TO bearing and that pushes the fluid back up to the master cylinder....what causes any clearance between the TO bearing and the pressure plate?
A return spring working against the slave cylinder to "return" it and the clutch fork to its set position. The exact same as a mechanical Z bar arraignment
what about mcleod throwout bearing???....think is good setup..just never used.. http://www.mcleodracing.com/products/1300+Series.+Bearing+Only.mcl
Depends on the type. I'm not sure if you may be looking to retrofit a newer transmission, but yes, on most newer factory stuff, the throwout bearing/slave combo, has constant contact.
So the question remains, are the TO bearings used with factory hydraulic setups any different to allow them to spin continuously or were early predictions of doom overly pessimistic?
With clutch fully engaged ( pedal up) there should be a speced clearance between the face of the TO bearing and the clutch fingers. 0.060 seems to be common. I have never seen nor heard anything remotely close to being any other way until your post. Curious as to how you reached your assumption?
Do not know about factory setups but the ones that I have seen installed in a few hot rods did not spin continuously. Pretty good info hear. see attached file http://www.cjponyparts.com/images/art/install_HCC5.pdf
There is NO clearance.....I repeat NO CLEARANCE. Depending on the style. You could be looking at better quality bearings, and or design/tolerances, designed for constant contact. Much like newer engines go for a lot more miles before rebuild. The life of a throwout bearing nowdays has a much longer expectancy. I feel a little offtopic going into this area, but to clear this up, here is a photo I hotlinked like an arsehole, from google images, of a new style throwout/slave combo. You will notice there is a spring behind the throwout bearing, coming from the face of the unit. That spring keeps the bearing constantly IN CONTACT WITH THE CLUTCH FINGERS. Its not a heavy spring, but yes, they do spin constantly. When you connect the transmission, it compresses that spring, and it stays compressed, untill the pedal is pushed. The position of the bearing in the picture is fully extended.
^^x2 never seen that before! Zero would be the speced clearance on that unit. Hey phucker how many and what manufactures use that? OEM or after market ?
I had one that specified a .035 preload, but After about 500 miles, the clutch began to slip. Called the manufacturer and they said to pull the shims, so I got both answers on the same part.
"riding the clutch" is what I always heard it called..... if you think about it for just a few minutes, you will figure out it is another old wives tale. I don't think the riding the clutch issue had anything to do with the throwout bearing. The belief was it was causing the clutch to slip and wear out. How far down do you have to push the pedal to get it to slip? Be a little uncomfortable driving with that much pressure on the pedal would't it? Think about how long wheel bearings last. They have pressure on them even sitting still. Differential bearings? The throwout bearing on MOST hydraulic clutches are in constant contact (never saw a factory one that wasn't) and that is the reason you NEVER have to adjust the clutch. Just like a 4 wheel disc brake car, the pedal remains the same no matter how thick (or thin) the pads are. 4 wheel drum car that retracts the shoes by springs.... remember the manual adjusted shoes? If they get out of adjustment (from wear) the pedal gets real low, adjust the brakes and the pedal comes back up. Why ? The pedal doesn't have to travel as far to expand the shoes. Ram has a bearing clearance? Finish the story..... they have that "hydraulic adjuster" in line to the slave to give you the "feel" of having a little free play. You have to keep adjusting it as the clutch wears.... just like a mechanical linkage. SO they aren't doing it to keep the bearing from wearing out.
Yes, difficult for we old guys to wrap our head around a throwout bearing which is pushing hard against the pressure plate all the time. That spring behind the pictured bearing is a stiff sucker. I used one in my Packard V8 in my Stude truck. So far, so good. jack vines
The Ram one I'm using fully retracts when your off the pedal, and is setup with .125-.200 clearance. Tech sheet: http://www.ramclutches.com/Instructions/RAM Hyd Setup.htm
That is only to set it up with the correct clearance so it won't over travel. It will be touching the bearing all the time once the clutch is bled and been pushed down 1 time.
From the installation instructions for that product: "This hydraulic bearing is designed with a constant running bearing that will touch the fingers of the clutch at all times, but does not apply pressure when the clutch is engaged."
The manufacturers logo on that baby is AP for AP Racing, a UK manufacturer of racing and aftermarket upgrades, mainly brake and clutch stuff. Chris
I used that McLeod hyd t/o bearing setup, it worked great, and was trouble free. The OEM's (Ford, GM, Chrysler) have been using the same style of hyd t/o bearing as shown in the picture for many years now. Had to replace the one in my OT 97 Ford F150 at around 285,000 miles because the seal in it started seeping a little (I'm still running the original clutch, and pressure plate at close to 360,000 miles).
My McLoed Hydraulic T/O bearing is in constant contact with the pressure plate figures. The constant forward pressure caused the back end of the crankshaft to have forward pressure on it and caused the crank main bearing thrust surface to wear out. It took out all the crankshaft "end play".
The 60s model Ford pickups had clearance between the bearing and clutch forks. The hydraulic cyclinder travel never changed, you adjusted a rod just like mechanical linkage , to adjust the clutch. Bones
Only time I've seen that problem was with mechanical linkage with the proper free play in the pedal, cause was a bad oil filter (Fram).
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