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Understanding The Pressure Plate

NoVaGT

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I had a 2012 GT with the Track Pack, and the clutch pedal got heavier and heavier over time, until the clutch was replaced. It was explained to me then, that the pressure plate "fingers" had (I'm struggling to remember) either gotten softer or stiffer. So they replaced the clutch under warranty. The clutch was then light as a feather, like when I bought the car new.

It seems to me that for the clutch pedal to get stiffer, the pressure plate would have to get stiffer, but how could that happen? What would cause the metal of the pressure plate to stiffen? Heat? Wouldn't a pressure plate's metal fatigue over time, to where it didn't apply enough pressure to the clutch disc, and cause slippage?

Am I not understanding how a pressure plate works, which way the forces go?
[ame]

I'm asking for two reasons;

1. The clutch pedal on my current 2016 GT is getting stiffer, so I've scheduled an appointment with my dealership. I'm suspecting the same issue as with my 2012 GT. So, I want to be clear myself so I don't get fed a bunch of bullshit and told "it's fine, go away".

2. I'm trying to figure out if there's something about the way I shift/clutch that is causing this issue.

Thanks in advance for your help.
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Anthony 05 GT

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I've had clutches that I've installed for example, in my F350 I had years ago after installing a new Luk clutch the pedal was way too light. As the disc got some time breaking in the effort began to get stiffer. This has happened several times for me and I chalk it up to a slight geometry change as the disc wears.
 

TexasRebel

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you see those grey "fingers" that the throwout bearing presses against?

Those are levers that act against the springs squeezing the friction disk between the pressure plate and flywheel.

The force from the throwout bearing does not stay perpendicular to the lever-arm. As the friction disk and friction surfaces wear out and get thinner, it will change the geometry of the lever action slightly. This could be noticeable.
 

Mountain376

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I had a 2012 GT with the Track Pack, and the clutch pedal got heavier and heavier over time, until the clutch was replaced. It was explained to me then, that the pressure plate "fingers" had (I'm struggling to remember) either gotten softer or stiffer. So they replaced the clutch under warranty. The clutch was then light as a feather, like when I bought the car new.

It seems to me that for the clutch pedal to get stiffer, the pressure plate would have to get stiffer, but how could that happen? What would cause the metal of the pressure plate to stiffen? Heat? Wouldn't a pressure plate's metal fatigue over time, to where it didn't apply enough pressure to the clutch disc, and cause slippage?

Am I not understanding how a pressure plate works, which way the forces go?


I'm asking for two reasons;

1. The clutch pedal on my current 2016 GT is getting stiffer, so I've scheduled an appointment with my dealership. I'm suspecting the same issue as with my 2012 GT. So, I want to be clear myself so I don't get fed a bunch of bullshit and told "it's fine, go away".

2. I'm trying to figure out if there's something about the way I shift/clutch that is causing this issue.

Thanks in advance for your help.
-What kind of mileage was on the 2012's clutch?
-Why was it replaced? Just old?

Typically, a pressure plates "fingers" won't get softer, in the sense that you are likely thinking. The fingers are very stiff, and if anything, will break from fatigue (heat+cyclic loading). You aren't going to get work-hardening of the spring fingers, either, from the working environment of a clutch.

Lightly touched on by TexasRebel, what you are feeling is likely from the normal wear of the clutch disc friction material over time. What happens, is that, when the clutch disc wears, the thickness of the disc gets smaller, which will decrease the amount of space the clutch disc takes up between the pressure plate friction plate and the flywheel. This change in space causes the internals of the pressure plate (mainly the friction plate) to recess further into the pressure plate assembly, and, effectively, change the "work" (think of it as effort) needed to be done by the fingers to allow the plate to lift up and free the clutch disc.

In the simplest way, the fingers are having to move further to allow the friction plate to free the clutch. Some clutches have an automatic wear adjustment. The 2012 clutch did not, from what I remember. The 2016's, I am not sure, as the clutch assembly and flywheel all changed.

1. How many miles are on your 2016's clutch?
2. There is nothing with your shifting that will cause an issue with the clutch. Only how you actuate the clutch pedal will have some kind of effect on the clutch.
 
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NoVaGT

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The car is getting a new clutch, under warranty. The service guys at my dealership were great, listened, and got the replacement approved. My 2016 car has about 19K miles on it.

My 2012 car had about 30K miles on it when it was replaced under warranty. That pedal got really hard, like ridiculously hard, and it took three trips to my dealership for them to listen, and get the clutch replaced under warranty.

Yesterday I had the Service Manager pull out a new Mustang, and compare my pedal effort to it, so he could see the difference in pedal pressure. I didn't want it to take 3 trips and an ever-increasing pedal effort to finally get it replaced, and they were great about it.

What frustrates me is that I drive in what I believe is a very clutch-friendly manner. I keep the slippage to a minimum, don't ride the pedal, don't do burnouts or anything like that. But maybe these cars just go through clutches and their friction material faster.

I've driven manual transmissioned cars for all of my 32 years of driving, and out of all those cars, I had only replaced one clutch due to wear (1988 Prelude with 180,000 miles on it) before these last two Mustangs. Both of which went bad waaaaay too early, AFAIC.
 

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Mountain376

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The car is getting a new clutch, under warranty. The service guys at my dealership were great, listened, and got the replacement approved. My 2016 car has about 19K miles on it.

My 2012 car had about 30K miles on it when it was replaced under warranty. That pedal got really hard, like ridiculously hard, and it took three trips to my dealership for them to listen, and get the clutch replaced under warranty.

Yesterday I had the Service Manager pull out a new Mustang, and compare my pedal effort to it, so he could see the difference in pedal pressure. I didn't want it to take 3 trips and an ever-increasing pedal effort to finally get it replaced, and they were great about it.

What frustrates me is that I drive in what I believe is a very clutch-friendly manner. I keep the slippage to a minimum, don't ride the pedal, don't do burnouts or anything like that. But maybe these cars just go through clutches and their friction material faster.

I've driven manual transmissioned cars for all of my 32 years of driving, and out of all those cars, I had only replaced one clutch due to wear (1988 Prelude with 180,000 miles on it) before these last two Mustangs. Both of which went bad waaaaay too early, AFAIC.
Weird, as I put 40k+ miles on my ‘12 GT of HPDE, time trials, autocross and daily driving on the stock clutch with zero issues (other than high-RPM lockout here and there). The guy who bought my car still has the stock clutch, as far as I know...

A stock clutch should last way past 60k miles in normal driving. I’ve taken many (in general) to 120k+. Easily at least around 40k with harder driving...

Edit: I remember there was an issue with 2011-early 2012 clutches and their pressure plate bolts backing out, causing transmission grinding/engagement issues, and sometimes giving a slightly harder pedal feel. There was also an update in 2012 to the Boss clutch bolt pattern but I forget the technical reasons Ford did that - I believe it was due to high RPM stability of the clutch.
 

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The car is getting a new clutch, under warranty. The service guys at my dealership were great, listened, and got the replacement approved. My 2016 car has about 19K miles on it.

My 2012 car had about 30K miles on it when it was replaced under warranty. That pedal got really hard, like ridiculously hard, and it took three trips to my dealership for them to listen, and get the clutch replaced under warranty.

Yesterday I had the Service Manager pull out a new Mustang, and compare my pedal effort to it, so he could see the difference in pedal pressure. I didn't want it to take 3 trips and an ever-increasing pedal effort to finally get it replaced, and they were great about it.

What frustrates me is that I drive in what I believe is a very clutch-friendly manner. I keep the slippage to a minimum, don't ride the pedal, don't do burnouts or anything like that. But maybe these cars just go through clutches and their friction material faster.

I've driven manual transmissioned cars for all of my 32 years of driving, and out of all those cars, I had only replaced one clutch due to wear (1988 Prelude with 180,000 miles on it) before these last two Mustangs. Both of which went bad waaaaay too early, AFAIC.
Almost 60k on my '16. Can't say its any different than mile 300.
135k on my pickup... factory clutch.

Must be an anomaly. You do make use of the dead-pedal, right?
 
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Weird, as I put 40k+ miles on my ‘12 GT of HPDE, time trials, autocross and daily driving on the stock clutch with zero issues (other than high-RPM lockout here and there). The guy who bought my car still has the stock clutch, as far as I know...

A stock clutch should last way past 60k miles in normal driving. I’ve taken many (in general) to 120k+. Easily at least around 40k with harder driving...

Edit: I remember there was an issue with 2011-early 2012 clutches and their pressure plate bolts backing out, causing transmission grinding/engagement issues, and sometimes giving a slightly harder pedal feel. There was also an update in 2012 to the Boss clutch bolt pattern but I forget the technical reasons Ford did that - I believe it was due to high RPM stability of the clutch.
Yeah, I'm puzzled. I just can't figure out why this has happened a 2nd time. But maybe it's not the clutch this time, or some other issue with the clutch assembly. Dunno.

Almost 60k on my '16. Can't say its any different than mile 300.
135k on my pickup... factory clutch.

Must be an anomaly. You do make use of the dead-pedal, right?
I don't ride the clutch pedal, at all. I do believe I drive in a clutch-friendly manner, minimal slippage, no burnouts, no clutch riding.

But something is going on. Very frustrated.
 
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NoVaGT

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Got the car back.

The system wasn't bled properly, but it self-bled over the last few days of driving. The pedal is lighter, but I'm not sure it's as light as it should be.

The horn works now though.
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