Throwout Bearing Wear

Read the FAQ and still not sure about something? Want to shift faster? Post here.
Post Reply
User avatar
ClutchFork
Master Standardshifter
Posts: 1515
Joined: Wed Mar 06, 2013 2:55 pm
Cars: 2001 S10 2.0L manual
Location: Detroit MI

Throwout Bearing Wear

Post by ClutchFork » Sun Sep 02, 2018 8:55 pm

So when I was growing up in the 1970s there were a lot more standard transmissions and few if any were hydraulic clutch linkage. Well the common warning back then was "don't keep the clutch pedal depressed sitting at a light, it will wear out the throwout bearing." Nowadays, I guess it is called a release bearing, but in more modern times most cars having hydraulic clutch linkage, I hear stuff like, "it doesn't matter if you keep the clutch pedal depressed at a light, it won't wear out the release bearing, they are always spinning anyway."

So, the practical application comes in since ClutchDisc and I have this 1992 Mustang with mechanical linkage and a real clutch fork. I am wondering if the old advice applies to this old school car.
Stick shiftin since '77
theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...

User avatar
tankinbeans
Master Standardshifter
Posts: 3837
Joined: Tue Apr 26, 2011 9:04 pm
Cars: 17 Mazda6, 03 Century
Location: Shakopee, MN

Re: Throwout Bearing Wear

Post by tankinbeans » Sun Sep 02, 2018 9:24 pm

I too hear conflicting stories regarding holding the clutch in at lights versus keeping it out. There are a couple YouTube channels I follow with conflicting opinions, not counting the poorly done ones with Joes Schmo off the streets.

I'm genuinely curious about the answers.
17 Mazda6
03 Century
InlinePaul wrote:The driving force of new fangled features to sell more cars [is to] cater to the masses' abject laziness!
Image

Rope-Pusher
Master Standardshifter
Posts: 10638
Joined: Mon Mar 16, 2009 3:44 pm
Cars: '08 Jeep Liberty
Location: Greater Detroit Area

Re: Throwout Bearing Wear

Post by Rope-Pusher » Mon Sep 03, 2018 12:38 pm

Seems tummy the factory uses a self-adjusting clutch cable on your musclestang. That will mean that the clutch release bearing is always in contact with the fingers on the clutch cover diaphragm spring, so whenever the engine is spinning, the bearing will be spinning.

That being said, the bearing loads are typically low until you depress the clutch pedal. Then the load increases and the bearing will start doing some work and running a bit warmer. How warm? That depends on the load, how many rippems, and how long you hold it in this position.

Eyed stink that at idle, even waiting at a relatively long-to-change traffic signal, the bearing wouldn't heat up to any temperature it wasn't designed to endure.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"

User avatar
ClutchFork
Master Standardshifter
Posts: 1515
Joined: Wed Mar 06, 2013 2:55 pm
Cars: 2001 S10 2.0L manual
Location: Detroit MI

Re: Throwout Bearing Wear

Post by ClutchFork » Wed Sep 05, 2018 8:58 am

The made-in-Israel clutch cable the previous owner had installed snapped on us. We had a made-in-USA cable installed. The instructions suggest it is not self adjusting as they state,
Remember to periodically readjust the clutch
cable tension as the clutch wears. This is very
important. As the clutch friction disc wears, the
clutch cable will become tighter, engaging the
clutch more and more. If the cable tension is not
reduced as the clutch wears, the clutch will
eventually start slipping, which leads to greater
wear, more cable tension and even faster wear.
Nonetheless, I think you are right and I will avoid prolonged depressed pedal situations.

FYI, This is the cable we had installed into the Mustang:
https://www.maximummotorsports.com/MM-C ... -P897.aspx



ANOTHER QUESTION (and related):

The input shaft to the tranny. When is it spinning in the pilot bearing. I think it makes sense to me that the only time the input shaft is spinning at the same speed as the pilot bearing is when the clutch is engaged. So that means only with the pedal depressed would the pilot bearing (and the throwout bearing) be subject to higher levels of wear. So now we have two good reasons to not hold the clutch pedal down for unnecessarily long times.

BUT I guess there is no answer (or no difference) in throwout wear between hydraulic and mechanical linkage, so maybe the difference is between clutch fork vs concentric slave?
Stick shiftin since '77
theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...

User avatar
theholycow
Master Standardshifter
Posts: 16004
Joined: Tue Jun 24, 2008 1:36 pm
Cars: '80 Buick LeSabre 4.1 5MT
Location: Glocester, RI
Contact:

Re: Throwout Bearing Wear

Post by theholycow » Tue Sep 11, 2018 4:21 pm

Lots of parts, especially for old cars and especially for stuff like clutches, come with a very generic sheet of instructions like that, with no indication that they may not apply to the part in your hand. That's not to say that it is self-adjusting, but I wouldn't take that sheet as gospel that it isn't.

Fork vs. concentric is irrelevant to this question. The bearing still exists and is similar/same. The self-adjusting nature of the hydraulic system works the same and produces the same result - relatively light load on the bearing when clutch engaged, heavier load when declutched.

You've been driving with clutches a hell of a lot longer than most of us here; have you ever regretted habitually standing on the pedal at red lights?

I don't think I've managed to wear out a release bearing.

Does the 'stang have a pilot bearing or a pilot bushing?

I wore a pilot bushing down to a sliver (leaving a severely oversized center hole, of course) in something like 90,000 miles after converting my car. A contributing factor, if not the entire cause, was the hacky conversion and mistakes I made with it (especially the way I modified the bushing, as well as improper preload on the input shaft bearing allowing the input shaft to flop around except as supported by the pilot bushing...but self-loosening bolts were part of it too). In driving I certainly was not gentle or careful with it and, after it proved itself, I never feared to abuse it. I didn't hesitate to stay declutched, and sometimes when there was one malfunction or another I had to stay declutched an awful lot. Despite all of that the pilot bushing lasted far longer than I ever expected any part of the system to last.

Also it's quite likely that my system routinely put more force into the release bearing, both under normal hydraulic self-adjusting preload and when declutched...but when I took it apart 90,000 miles later the release bearing seemed fine.
1980 Buick LeSabre 4.1L 5MT

Put your car in your sig!

Learn to launch/FAQs/lugging/misused terms: meta-sig
watkins wrote:Humans have rear-biased AWD. Cows have 4WD

User avatar
ClutchFork
Master Standardshifter
Posts: 1515
Joined: Wed Mar 06, 2013 2:55 pm
Cars: 2001 S10 2.0L manual
Location: Detroit MI

Re: Throwout Bearing Wear

Post by ClutchFork » Tue Sep 11, 2018 10:23 pm

Well I have habitually not kept it in gear at lights because it seemed nicer to just sit there with light brake pressure than heavier clutch pressure. If the throwout warning was any influence against my trying to keep it engaged at a light, I don't know, but there was that general fear and reluctance to keep the pedal down for very long.

My only throwout bearing issue was the Ford Ranger. A year after I got it the slave leaked. They installed a new slave (but left the original throw-out that was in there). One year later to the week, if not the day, I went to mash the clutch pedal and it was like a fixed bracket. Would not go down for all the force I could give it. It was a failed throw-out bearing. But that Ranger was just a clutch linkage nightmare anyway. Good riddance. I am much happier with the S-10.

But the Mustang is great with the mechanical linkage. I wonder if they make kits to covert hydraulic to mechanical? Probably require getting an old tranny with the fork hole and mount in the bell housing or something. It would be great though.
Does the 'stang have a pilot bearing or a pilot bushing?
Well now you have thrown me a curve. I did not realize this was done two ways. Presumably a bushing and that is what I meant in my earlier post.
Stick shiftin since '77
theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...

User avatar
theholycow
Master Standardshifter
Posts: 16004
Joined: Tue Jun 24, 2008 1:36 pm
Cars: '80 Buick LeSabre 4.1 5MT
Location: Glocester, RI
Contact:

Re: Throwout Bearing Wear

Post by theholycow » Wed Sep 12, 2018 9:47 am

When I was doing my conversion I considered a mechanical linkage a little bit. Due to lack of information/products/prior art/knowledge/time/money I went with the hydraulic system from the S10. I never came across any mechanical linkage conversion kits.

With a fork-operated clutch it shouldn't be too hard to adapt a mechanical linkage from another vehicle, probably more tedious than difficult. IMO it wouldn't be worth the effort, though.
1980 Buick LeSabre 4.1L 5MT

Put your car in your sig!

Learn to launch/FAQs/lugging/misused terms: meta-sig
watkins wrote:Humans have rear-biased AWD. Cows have 4WD

User avatar
ClutchFork
Master Standardshifter
Posts: 1515
Joined: Wed Mar 06, 2013 2:55 pm
Cars: 2001 S10 2.0L manual
Location: Detroit MI

Re: Throwout Bearing Wear

Post by ClutchFork » Wed Sep 12, 2018 4:22 pm

theholycow wrote:
Wed Sep 12, 2018 9:47 am
When I was doing my conversion I considered a mechanical linkage a little bit. Due to lack of information/products/prior art/knowledge/time/money I went with the hydraulic system from the S10. I never came across any mechanical linkage conversion kits.
My s10 hydraulics work great. I think it is a big help that the master on the S10 is dead level in the firewall, where as the stupid mounting for the Ranger has it on a steep incline so it is near impossible to bleed.
Stick shiftin since '77
theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...

Post Reply