Throw out bearing always makes contact?

[jhv48]

I wish I could forget this thread!

[Excaliber]

MOST of replicas have an after market clutch system, it's simple. Follow the manufacturers recommendation.

About the only guys that might have an OEM stock unit (Ford) would be a "donor" type build, like an FFR or maybe a Classic Roadster. Your first clue would be a "cable clutch". Many of those WITH a cable clutch either replace the cable with an adjustable after market unit or figure out how to get the clearance. Not everyone believes Ford has a better idea, especially when they just installed that new $500 after market clutch!

It's really not complicated at all, you need to follow the clutch manufacturers specifications (.100 to .300 clearance generally speaking, 1/4"). 95% of replicas will be running an aftermarket clutch.

[CobraEd]

much ado about nothing.


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[patrickt]

Originally Posted by CobraEd

much ado about nothing.

I agree. Even if you rag your TOB out so it only lasts 10k miles that means most of us will only end up changing it out once or twice in our lifetime. And even then it's a weekend job (an afternoon's job for ERAChas....).

[ERA Chas]

-and then head to the haberdasher...

[Excaliber]

...much ado about nothing.

Do you have a clue how often this question is asked, a new thread started? This is like the third one in the last month. The question comes around every few months. The easy and typical answer is "don't worry about it". The RIGHT answer is, "Ask the manufacturer of your clutch." Don't know who that is, don't know how to find out? Then the answer for you is "don't worry about it, your to stupid to fix it anyway."

[CobraEd]

Yes the question has been asked and the answer is that for most environments, this is not an issue. It is not a fuction of HP, but of throwout bearing/clutch design. Asking the question and getting the wrong answer by telling people to fix what is not broken are not the same thing. There are millions of cars in the world that have gone hundreds of thousands of miles like this with no issues.

Ford would not "overlook" this for decades and millions of cars. There have been no problems or recalls whatsoever.

Yes I istalled my own RAM aluminum SFI flywheel, Ford Racing King Cobra clutch and McLeod SFI rated bellhousing. Did you install yours?


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[Excaliber]

So what throw out bearing did you run Ed? OEM Ford? After market? Off the shelf from NAPA? It makes a difference. I've seen throw out bearings go out in as little 4,000 miles.

From the web site "ModedMustangs", where you can find plenty of threads about folks who have had to replace their throw out bearings in a few thousand miles.

Recently i had a king cobra clutch kit installed and after about 2500 miles the throw-out bearing started making noise.

[patrickt]

Originally Posted by Excaliber

Then the answer for you is "don't worry about it, your too stupid to fix it anyway."

Ernie -- I thought we were all trying to be nicer to one another.

[Excaliber]

I know Pat, I'll try one of the pink pills....

Sometimes, the truth hurts. Most of us could likely ignore the whole issue, but someone, somewhere IS going to get burned. Know the truth, then make an informed decision that your comfortable with.

[CobraEd]

I am going to recomend that everyone jump through their ass to replace their throttle cables with drive by wire systems. There have been reports that due to the inner cable and outer sheath of the throttle cable rubbing together during throttle use, there is a chance that the cable could wear out after 1,000,000,000 miles. THIS IS UNACCEPTABLE !!!!!!



Sorry, . . . I had to do it !!


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[stallion112]

I work for one of the companies that design, validate, and manufacture clutch release bearings for the OEM and aftermarket so I may be able to shed some light on this subject.

The primary factor that determines whether or not a clutch release bearing is preloaded or not, is the design of the bearing.

A century ago, bronze or carbon cartridges were mounted in a cast iron or forged trunnion. This design resulted in a high level of wear.

In the early 1930’s, anti-friction ball bearings began to replace the bronze and carbon cartridges. By the mid to late 1930’s, a fixed guide tube was introduced to help stabilize the clutch release system.

Most of the improvements in the 1940’s and 50’s were a result of better greases and seal materials.

In 1967, a patent was issued for a self-centering clutch release bearing. This enabled the bearing to find its own axis of rotation with relation to the clutch diaphragm spring. This type of bearing design requires a light preload in order to maintain concentricity of the rolling elements and raceways as an assembly. With the previous designs, when the bearing assembly was unloaded as the clutch pedal was released, the relationship (concentricity) of the two raceways was lost. What this meant was that each time the pedal was pressed and the bearing was loaded, the raceways (and rolling elements) were on their own axis of rotation during the initial operation of the bearing. Eventually, concentricity of the rolling elements and the raceways would be restored but only after sliding and friction (wear and heat) had occurred.

The result of the self-centering release bearing was a reduction in bearing operating temperatures by 25%, and an increase of service life by 400% over then-current designs. This type of a bearing was first used on several high-volume European models in the late 1970’s – early 1980’s. Its introduction to the North American market was in the late 1980’s – early 1990’s.

Long gone are the days when a part can be swapped from one vehicle to another and be expected to work with a high level of confidence. For many years, OEM’s have developed each part and assembly around a very narrow set of design criteria that are based on a drivers perceptions, service life, governmental regulations, etc. In the case of clutch release bearings that have been designed to operate with preload, certain Ford applications in particular, have been used successfully for many years. There have been problems with the release mechanism itself such as the one used on the old Fox body Mustang’s but, that design has been obsolete for years.

When the Ford technicians say that the clutch release bearings on certain models are designed to operate with preload and no clearance, they are 100 percent correct. This statement obviously does not apply across the board to every clutch release bearing on the market, particularly those used in the aftermarket. Again, whether or not a bearing operates with clearance depends on the way the system is designed, more specifically, which type of bearing is being used. For example, there have been comparisons to wheel bearings in previous postings to this thread. It's a good point. Keep in mind that wheel bearings are designed to be in constant rotation. The old release bearings were not. That's why if they were in constant rotation it wasn't long before they would grenade.

[lal Naja]

Stallion112,

Thanks for the enlightening TOB historical report. It is based on your post that I now feel confident about the pre-load on my TOB.

Arthur

[lovehamr]

Stallion112, I gotta ask, cause I'm ignant', how can we tell the difference?

Steve

[strictlypersonl]

Stallion,

Thanks! That was quite enlightening.

I checked a couple of our typical TO bearings here:

RAM 486 (Weber 16042) for Big-spline Toploader: Floating face

Fed. Mogul 614038, Small-spline TL and Tremec: Floating face

That would imply both should be used with zero clearance...

[Excaliber]

This from the Ram web site regarding setting up the 4800 series throw out bearing:

If the proper release gap is not attained, you must remove the bellhousing, disconnect the hydraulic lines, loosen the set screw and turn the bearing cylinder in or out until the proper release gap and/or air gap is found. This may take several tries, but take the time now to get it right!

Instructions for my recently installed Ram clutch specified .250 clearance. That setup is the classic external slave hydraulic application, like most ERA's run. Implied isn't good enough for me. I want to know specifically what the manufacturer of the throw out bearing itself specifies. Clutch finger clearance, or not.

[mpanten]

Originally Posted by Excaliber

This from the Ram web site regarding setting up the 4800 series throw out bearing:



Instructions for my recently installed Ram clutch specified .250 clearance. That setup is the classic external slave hydraulic application, like most ERA's run. Implied isn't good enough for me. I want to know specifically what the manufacturer of the throw out bearing itself specifies. Clutch finger clearance, or not.

I think the clutch manfacturer's and slave manafactures need to get together. There is no way and I mean no way I can have .250 clearence and still get enough throw to disengage the clutch. I have tried for weeks and and spent countless hours. Maybe it's beacuse im running a twin disc and it needs more throw than a single disc but I can say with complete confidence that in my case it aint happening

[Excaliber]

Thats a good point about the cltuch vs the throw out bearing supplier. The final specification would HAVE to come from the throw out bearing manufacturer because only HE knows what style your using!

If it's made in China, all bets are off.

Twin disc is a different animal all right. Depth of the input shaft is critical, for instance. The trans throw out bearing collar may even need to be modified by grinding away a portion of it external base to allow for more travel of the throw out bearing.

Some throw out bearings do use a bearing assembly just like a front wheel bearing, tapered roller bearings. Other use ball bearings. It should be obvious which style you could run zero clearance with, or not.

[mpanten]

I would soon as cut my right arm off rather than take that transmission out again If I get a few years out of this set up I will be happy. I almost went back to the hydraulic throw out set up.

[Excaliber]

Ha Ha, man I hear that. I've had my trans out SO many times I'm almost burned out. One time was to replace, wait for it, a bad throw out bearing which had been running with zero clearance and burned up. That took about 7,000 miles.