TheLion70x77
Well-Known Member
- Thread starter
- #1
Since you can add me to the list of GT owners who have fried a stock clutch without ever drag racing in 30k or less...I did some more digging have come to following conclusions:
Some GT owners, going all the way back to the introduction of the Coyote 5.0 in the 2011 S197 mustangs and later the 2013-2014 Boss 302 track variants, experience an issue during WOT and high RPM shifting, where the clutch pedal does not return at all or partially and slowly returns. Most of these cars also experience clutch failure at relatively low mileages, despite most owners significant past experiences driving a manual transmission car.
For reference, my previous car (prior to getting into Mustangs), was a 2007 Focus St 5M with 175,000 miles on the original clutch and I beat on that car every day. I used it for hauling mulch to my home, camping, going on trips and driving it hard on the twisties etc. The clutch got a workout and over many miles without failure.
Symptoms are clutch pedal does not return during high RPM shifting and when it does, it often only partially or very slowly returns, burning smell (like hot brakes) and eventually delamination of the organic friction pads on the clutch disk. When that occurs, the pedal may travel to the floor and never return or in my case, the pedal went very soft, as in no resistance because the clutch is stuck "open" from the chunks of delaminated friction pad wedging it open as they fell off, so the slave likely wasn't even touching the pressure plate fingers at that point. I confirmed with the dealer the slave is operation and was not damaged, so the clutch itself is failure point and not he salve blowing out as I originally suspected and hoped for (in that case, I could argue the salve caused damaged to the clutch disk by causing inadequate movement of the pressure plate).
I have seen theories and even statements by Ford that the issue is a result of centripetal forces acting on the clutch, think gyroscope, which prevent it from easily moving at high RPM. Some people report that after market clutches cured that issue, but interestingly many of them also upgrade the hydraulic line as well because it's known to cause issues when hot. Not all GT owners experience this issue or experience to the severity it's noticeable or problematic to them, but many do. Even some Ecoboost Mustang owners have experienced this problem, especially during track use with big turbos.
The most unlikely source has lead to a new theory. User reviews of the upgraded clutch lines from SR, Steeda, Ford Performance and McLeod. All four of them make upgraded clutch hydraulic lines for S197's and S550's. Nearly every review has reports of significantly improved engagement, especially during WOT at High RPMs on both the stock clutch and after market clutches. And about half of them report that replacing just the hydraulic line actually cured their high RPM pedal issues without any clutch replacement, some reviews don't mention the high rpm pedal travel issue at all, but seem to indicate a notable improvement in engagement feel and linearity.
I've come to the conclusion that the OE clutch is not the issue in the majority of cases and is a fairly robust unit, especially since many report the stock clutch taking the abuse of a super charger for tens of thousands of miles before failure or examples like Braski's Project Midnight that saw two years of drag racing with 5,500 RPM launches on DR"s with a Power Pack 2...either of those cases produce substantially more stress on the clutch and road race, daily driving or auto x. We have multiple factors at work here that are all related to the factory plastic line:
1. It shares fluid from the brake reservoir, for track guys, heating up the brake fluid will likely cause some thermal transfer to the clutch hydraulic fluid as they share the same reservoir.
2. The line is located inside the engine compartment and passes by the headers. During heavy throttle uses, even for short duration, the line is in a compartment that sees high temperatures and is near a heat source producing temperatures in excess of 1,500 degrees...
3. The line is polymer and will flex or bulge even during normal operation, but when exposed to extreme thermal loads, bulges enough to cause inadequate slave cylinder operation, resulting in high clutch slip during shifting (it's not disengaging the clutch fully, so it's heating up a lot as you shift).
4. As the clutch heats up, the fluid and slave is exposed to even more heat from the clutch disk getting extremely hot, obviously it transfers some heat to the output shaft, fingers and pressure plate. The output shaft and fingers are in direct contact with the slave. This also thermally fatigues the organic friction pads which begin to wear rapidly and may fire crack. Once that occurs they delaminate as the friction pad is one continuous ring on each side and needs to be intact for strength. Any cracks will cause inadequate support and further cracking of the friction pad rings.
This also explains the mysterious burning smell I experience after hard driving, which I have always thought to be the brake pads, but may very well have been the factory clutch over heating. I have never found an oil or fluid leak anywhere nor has the dealer. Everything is dry as a bone. No fluid loss either. That leaves the brakes, clutch or anything exposed to high temperatures.
I suspect the clutch issues have far more to do with the hydraulic line bulging and consequently not providing proper pressure to the slave which over heats the clutch than centripetal forces preventing the clutch from opening and closing. Honda manages to have proper clutch operation on their S2000's which rev out to 9,000 RPM...the GT350's doesn't have wide spread issues with the clutch operating properly out to 8,250 RPM...why the GT would have issues at just 6,800 RPM stock or 7,150 to 7,450 RPM with a power pack is beyond me unless the design is that inferior...
Any why Ford Performance would offer a braided SS / hard clutch hydraulic line specifically to deal with heat related issues screams to me that they know it's an issue but aren't willing to absorb the cost of using a solid stainless or braided stainless line because the average driver doesn't push the car hard enough to cause failures, despite the fact that many enthusiasts have paid the price...literally.
Some GT owners, going all the way back to the introduction of the Coyote 5.0 in the 2011 S197 mustangs and later the 2013-2014 Boss 302 track variants, experience an issue during WOT and high RPM shifting, where the clutch pedal does not return at all or partially and slowly returns. Most of these cars also experience clutch failure at relatively low mileages, despite most owners significant past experiences driving a manual transmission car.
For reference, my previous car (prior to getting into Mustangs), was a 2007 Focus St 5M with 175,000 miles on the original clutch and I beat on that car every day. I used it for hauling mulch to my home, camping, going on trips and driving it hard on the twisties etc. The clutch got a workout and over many miles without failure.
Symptoms are clutch pedal does not return during high RPM shifting and when it does, it often only partially or very slowly returns, burning smell (like hot brakes) and eventually delamination of the organic friction pads on the clutch disk. When that occurs, the pedal may travel to the floor and never return or in my case, the pedal went very soft, as in no resistance because the clutch is stuck "open" from the chunks of delaminated friction pad wedging it open as they fell off, so the slave likely wasn't even touching the pressure plate fingers at that point. I confirmed with the dealer the slave is operation and was not damaged, so the clutch itself is failure point and not he salve blowing out as I originally suspected and hoped for (in that case, I could argue the salve caused damaged to the clutch disk by causing inadequate movement of the pressure plate).
I have seen theories and even statements by Ford that the issue is a result of centripetal forces acting on the clutch, think gyroscope, which prevent it from easily moving at high RPM. Some people report that after market clutches cured that issue, but interestingly many of them also upgrade the hydraulic line as well because it's known to cause issues when hot. Not all GT owners experience this issue or experience to the severity it's noticeable or problematic to them, but many do. Even some Ecoboost Mustang owners have experienced this problem, especially during track use with big turbos.
The most unlikely source has lead to a new theory. User reviews of the upgraded clutch lines from SR, Steeda, Ford Performance and McLeod. All four of them make upgraded clutch hydraulic lines for S197's and S550's. Nearly every review has reports of significantly improved engagement, especially during WOT at High RPMs on both the stock clutch and after market clutches. And about half of them report that replacing just the hydraulic line actually cured their high RPM pedal issues without any clutch replacement, some reviews don't mention the high rpm pedal travel issue at all, but seem to indicate a notable improvement in engagement feel and linearity.
I've come to the conclusion that the OE clutch is not the issue in the majority of cases and is a fairly robust unit, especially since many report the stock clutch taking the abuse of a super charger for tens of thousands of miles before failure or examples like Braski's Project Midnight that saw two years of drag racing with 5,500 RPM launches on DR"s with a Power Pack 2...either of those cases produce substantially more stress on the clutch and road race, daily driving or auto x. We have multiple factors at work here that are all related to the factory plastic line:
1. It shares fluid from the brake reservoir, for track guys, heating up the brake fluid will likely cause some thermal transfer to the clutch hydraulic fluid as they share the same reservoir.
2. The line is located inside the engine compartment and passes by the headers. During heavy throttle uses, even for short duration, the line is in a compartment that sees high temperatures and is near a heat source producing temperatures in excess of 1,500 degrees...
3. The line is polymer and will flex or bulge even during normal operation, but when exposed to extreme thermal loads, bulges enough to cause inadequate slave cylinder operation, resulting in high clutch slip during shifting (it's not disengaging the clutch fully, so it's heating up a lot as you shift).
4. As the clutch heats up, the fluid and slave is exposed to even more heat from the clutch disk getting extremely hot, obviously it transfers some heat to the output shaft, fingers and pressure plate. The output shaft and fingers are in direct contact with the slave. This also thermally fatigues the organic friction pads which begin to wear rapidly and may fire crack. Once that occurs they delaminate as the friction pad is one continuous ring on each side and needs to be intact for strength. Any cracks will cause inadequate support and further cracking of the friction pad rings.
This also explains the mysterious burning smell I experience after hard driving, which I have always thought to be the brake pads, but may very well have been the factory clutch over heating. I have never found an oil or fluid leak anywhere nor has the dealer. Everything is dry as a bone. No fluid loss either. That leaves the brakes, clutch or anything exposed to high temperatures.
I suspect the clutch issues have far more to do with the hydraulic line bulging and consequently not providing proper pressure to the slave which over heats the clutch than centripetal forces preventing the clutch from opening and closing. Honda manages to have proper clutch operation on their S2000's which rev out to 9,000 RPM...the GT350's doesn't have wide spread issues with the clutch operating properly out to 8,250 RPM...why the GT would have issues at just 6,800 RPM stock or 7,150 to 7,450 RPM with a power pack is beyond me unless the design is that inferior...
Any why Ford Performance would offer a braided SS / hard clutch hydraulic line specifically to deal with heat related issues screams to me that they know it's an issue but aren't willing to absorb the cost of using a solid stainless or braided stainless line because the average driver doesn't push the car hard enough to cause failures, despite the fact that many enthusiasts have paid the price...literally.
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