Boss Transmission/Clutch Issues Poll Discussion Thread

[isrboss]

I applaud the fact that some will never quit trying to find a better way, but I'm not finding breakthroughs here in reliability. The flip side is if manufactures keep having their vehicles on their lifts for the same issue, they usually apply a fix to the troubled area/part. I don't see this happening for the trans/clutch problem though. The GT500's, Mustangs/Boss and others say R/S's have it as well, so it does appear the aftermarket is going to need to step up and fix this for us. The spring is not the fix(for some), the clutch is not the fix(for some). My guess would have to be the hydraulics is the real fix. I don't think it would be all that hard for some of you to just add a separate reservoir to the clutch, block off the fittings on the brake reservoir and see what happens. That would be a good place to start, what do you guys think, is that a doable test?

 

[JB]

I pulled my clutch spring yesterday. I cant say that I feel the engagement point any better because I didnt have issues with that in the past, but the clutch is definetely heavier. I did notice that odness of the clutch at a 7400rpm shift seems to be gone, but my clutch has never fully stuck to the floor, its just felt strange at that rpm.

 

[athens7]

After 17,000 miles and 9 track days of trouble free clutch operation, I got the spongy, returns only halfway clutch pedal, coupled with 4-5 lockout (twice) and 3-4 lockout (once), first at Roebling Road (once) on a hot, sunny day during the 4th 20 minute session, then at Road Atlanta (twice) on a cloudy, 80 degree day after rain during the 2nd 20 minute session. It did not stick to the floor in any case. The Roebling episode included an occurrence as I was leaving the track for the paddock, so low rpms and less than 20 mph. The Road Atlanta occurrences were at full song on the back straight.

The car will go to the dealer next week for an oil change, brake fluid replacement, and this clutch issue. Btw, I have run Super Blue DOT 4 in the car since it was 2 months old, right after the first track day. I am now switching to Motul RBF 600. I have bled the clutch regularly, using a vacuum pump and adapter, per Ford service bulletin.

I have read this thread, as well as others here and on other forums. It's apparent to me that there is some fundamental design flaw in the Mustang clutch assembly, as this problem has existed for several years and predates the Boss. I have some questions for those smarter/more skilled/more experienced than me, and am trying to coalesce the things I've read in order to get my wee brain around them and try to determine a path forward.

• The problem typically stems from over 7000 rpm shifts
• Some cars suffer from this almost from day one, some develop it over time, and some may never develop it (can't be sure unless all Bosses are tested at high RPMs)
• The problem is not specific to the unique Boss clutch, as it occurs in GTs that are modified to allow higher RPM operation and have a different clutch
• While most occurrences involve higher heat environments, heat does not appear to be a necessary prerequisite
• Attempts to fix the issue have included: upgraded clutch lines, assist spring removal, aftermarket clutches, GT500 pedal assemblies. None of these have definitively been proven to address the problem
• Possible causes have included clutch diaphragm fingers, pressure plate bolts loosening, throwout bearing spring deficiencies (mentioned in one post as attributed to McLeod tech support), slave cylinder deficiencies, & possibly issues with shared hydraulics between clutch and brakes (I'm sure I'm missing some things)
• Ford's TSB 10-19-4 indicates replacement of the pedal assembly as the fix for this problem on cars built before 4/25/2010, which implies that cars built after this date have the new pedal assembly installed at the factory

With these items, as well as the efforts of people to address this issue as background, the following questions occur to me:

• Why does Rick's Mcleod clutch still have pedal issues with the assist spring in, while Justin's Centerforce does not? Is there some fundamental difference between the 2 clutch assemblies that one could point to as the cause for this?
• Has anyone replaced the slave cylinder and/or throwout bearing without replacing the clutch?
• If McLeod thinks the throwout bearing springs are a cause, do they recommend replacement as part of their clutch upgrade?
• Does anyone make an upgraded slave cylinder or throwout bearing? I believe Exedy does, but only for their clutch?
• Most people say the GT500 pedal assembly is simply the boss pedal assembly without the assist spring, but the pictures I've seen appear slightly different (the red cap on the upper left side of the assembly on the GT500 version, for example). Are the 2 assemblies in fact identical, except for the assist spring?
• There seems to be general agreement that the assist spring removal is treating the symptom, not the disease, and comes at the cost of harder clutch actuation. If a simple mechanical device were to blame, shouldn't the problem be easily duplicated?
• One poster mentioned the possibility of an alignment issue in the clutch assembly. Since some cars seem to have the issue right away, while others take time to develop, this seems to make sense. If the issue was one of decay, you wouldn't expect to see cars with the problem from the start. If the issue was one of substandard parts, all cars should display the problem in a consistent manner. Any thoughts on this?

I'm a salesman, not an engineer, so I lack the vocabulary and knowledge to solve this problem; I can only run my mouth . Having pursued a path similar to Rick's on previous cars (i.e., throw money and parts at the problem using the best information available to me), I know how costly and frustrating it can be. I also know I won't simply drive the car as the problem gets worse. Lastly, since it's my daily driver and most of my use is in town, I can't live with a competition clutch. So, if Ford (or someone else) would simply provide me with a clutch that feels just like the one I've got, only works as Ford represented, I'd be good to go! In the alternative, one last question:

Which aftermarket clutch/pedal assembly is closest in feel, friction point, and overall operation to the stock set up?

edit: I should mention I started heel/toe about 7 months ago, and practice daily, whether on street or track. I don't know if or how much this would affect clutch wear.

 

[isrboss]

athens, great recap!

I feel like you could do us all a great justice at this point. Since you now have 17,000+ miles and 9 track days on that OEM clutch and just started to experience the clutch pedal hanging. What I would do in this situation is to purchase the Ford Racing clutch line. It's larger and because of this will have more fluid in the line to help with disengagement. I'm thinking since the clutch disc has worn that the slave needs to come out further to disengage the pressure plate. To those that know, is this the case? After researching other manufacture vehicles with similar clutch issues, it appears manufactures purposely make the master cylinder small to prevent fast shifting. This supposedly cuts back on warranty, but wears clutches, which we know is coming out of our pocket to replace.

Give it a shot, Ford Racing is telling us something with that larger line. I am feeling confident that it is the master cylinder is not delivering enough fluid for high rpm/fast shifting, in return we are living it.

 

[athens7]

Are we talking about Ford Racing part # M-7512-A?

Also, much discussion exists on this thread about this clutch line only serving to protect from melting due to exhaust heat, rather than improving fluid transfer. Further, in my limited understanding of hydraulic fluid function, expansion of the line would cause reduced force, while constriction of the line would cause increased force, assuming limited fluid compression. If hydraulic fluid is basically a liquid cable pushing on a mechanism, how would the line affect the ability of the slave cylinder to extend further in order to disengage the clutch? Additionally, are we postulating that the plastic line degrades over time, becoming more prone to expansion? If so, how would that explain cars that display this condition almost immediately? Fun, huh? :

Edit: I just got off the phone with Ford Racing Technical support, who agreed the FR clutch line was a heat protection device, rather than an expansion control or fluid capacity device.

 

[isrboss]

Are we talking about Ford Racing part # M-7512-A?

Also, much discussion exists on this thread about this clutch line only serving to protect from melting due to exhaust heat, rather than improving fluid transfer. Further, in my limited understanding of hydraulic fluid function, expansion of the line would cause reduced force, while constriction of the line would cause increased force, assuming limited fluid compression. If hydraulic fluid is basically a liquid cable pushing on a mechanism, how would the line affect the ability of the slave cylinder to extend further in order to disengage the clutch? Additionally, are we postulating that the plastic line degrades over time, becoming more prone to expansion? If so, how would that explain cars that display this condition almost immediately? Fun, huh? :

Edit: I just got off the phone with Ford Racing Technical support, who agreed the FR clutch line was a heat protection device, rather than an expansion control or fluid capacity device.

I could have swore I read that the line was bigger than stock. Hmm my bad, so my theory just tumbled to the I don't have a clue.
Edit I thank you for this discussion, as it remided me I had to bleed the clutch. 3 track days 3000 miles and 3 clutch bleeds. I do 3 reservoir empties and refills with fresh DOT 4 everytime, so I have 9 bleeds actually.

 

[VTBoss302]

Time to price out a Tremec...

After 17,000 miles and 9 track days of trouble free clutch operation, I got the spongy, returns only halfway clutch pedal, coupled with 4-5 lockout (twice) and 3-4 lockout (once), first at Roebling Road (once) on a hot, sunny day during the 4th 20 minute session, then at Road Atlanta (twice) on a cloudy, 80 degree day after rain during the 2nd 20 minute session.

You have found the Boss' achilles heel...

New clutch might help, but..

If money is no object look into a Boss 302R, 2013+ Gt500 and/or Tremec XL.

 

[Justin]

With these items, as well as the efforts of people to address this issue as background, the following questions occur to me:

• Why does Rick's Mcleod clutch still have pedal issues with the assist spring in, while Justin's Centerforce does not? Is there some fundamental difference between the 2 clutch assemblies that one could point to as the cause for this?
• Has anyone replaced the slave cylinder and/or throwout bearing without replacing the clutch?
• If McLeod thinks the throwout bearing springs are a cause, do they recommend replacement as part of their clutch upgrade?
• Does anyone make an upgraded slave cylinder or throwout bearing? I believe Exedy does, but only for their clutch?
• Most people say the GT500 pedal assembly is simply the boss pedal assembly without the assist spring, but the pictures I've seen appear slightly different (the red cap on the upper left side of the assembly on the GT500 version, for example). Are the 2 assemblies in fact identical, except for the assist spring?
• There seems to be general agreement that the assist spring removal is treating the symptom, not the disease, and comes at the cost of harder clutch actuation. If a simple mechanical device were to blame, shouldn't the problem be easily duplicated?
• One poster mentioned the possibility of an alignment issue in the clutch assembly. Since some cars seem to have the issue right away, while others take time to develop, this seems to make sense. If the issue was one of decay, you wouldn't expect to see cars with the problem from the start. If the issue was one of substandard parts, all cars should display the problem in a consistent manner. Any thoughts on this?

I'm a salesman, not an engineer, so I lack the vocabulary and knowledge to solve this problem; I can only run my mouth . Having pursued a path similar to Rick's on previous cars (i.e., throw money and parts at the problem using the best information available to me), I know how costly and frustrating it can be. I also know I won't simply drive the car as the problem gets worse. Lastly, since it's my daily driver and most of my use is in town, I can't live with a competition clutch. So, if Ford (or someone else) would simply provide me with a clutch that feels just like the one I've got, only works as Ford represented, I'd be good to go! In the alternative, one last question:

Which aftermarket clutch/pedal assembly is closest in feel, friction point, and overall operation to the stock set up?

edit: I should mention I started heel/toe about 7 months ago, and practice daily, whether on street or track. I don't know if or how much this would affect clutch wear.

The red cap you are seeing is part of the shipping of the GT500 assembly its removed once you install it. They are indeed the same thing minus the assist spring I verified to all the sub assembly part numbers.

Exedy does make an aftermarket slave cylinder but upon emailing them they told me it only works with their clutch(doesnt make sense to me but ok probably just trying to get me to buy their clutch).

The difference between the two mcleod and centerforce is quite a bit. Counterweights on the fingers to increase clamping at higher rpm, and the centerforce fingers rotate on ballbearings.

Its not an alighnment issue as the slave cylinder is free to center itself. I have one in a box that I have played with and the bearing has some movement in it.

The JHR heavy duty line is indeed larger. just search youtube "JHR clutch line" and he points out the differences.

The 2013 GT500's now come with that assist spring and low and behold they have the same issue as the rest of the mustangs with the assist spring.

I didnt like how the clutch felt with the spring removed with the factory clutch. with the centerforce and the spring removed its nearly identical to the stock clutch with the spring in amount of force to push the clutch in and just feels silky smooth.

I am a firm believer that the spring isnt helping the poorly designed clutch and the clutch needs to be replaced regardless. I would look to maybe a centerforce dual friction single disc clutch if you are on a budget but no promises that it will work as I havent tried that clutch in this car only previous mustangs.

 

[VTBoss302]

The red cap you are seeing is part of the shipping of the GT500 assembly its removed once you install it. They are indeed the same thing minus the assist spring I verified to all the sub assembly part numbers.

Exedy does make an aftermarket slave cylinder but upon emailing them they told me it only works with their clutch(doesnt make sense to me but ok probably just trying to get me to buy their clutch).

The difference between the two mcleod and centerforce is quite a bit. Counterweights on the fingers to increase clamping at higher rpm, and the centerforce fingers rotate on ballbearings.

Its not an alighnment issue as the slave cylinder is free to center itself. I have one in a box that I have played with and the bearing has some movement in it.

The JHR heavy duty line is indeed larger. just search youtube "JHR clutch line" and he points out the differences.

The 2013 GT500's now come with that assist spring and low and behold they have the same issue as the rest of the mustangs with the assist spring.

I didnt like how the clutch felt with the spring removed with the factory clutch. with the centerforce and the spring removed its nearly identical to the stock clutch with the spring in amount of force to push the clutch in and just feels silky smooth.

I am a firm believer that the spring isnt helping the poorly designed clutch and the clutch needs to be replaced regardless. I would look to maybe a centerforce dual friction single disc clutch if you are on a budget but no promises that it will work as I havent tried that clutch in this car only previous mustangs.

Solid real world info.

I also have the GT500 pedal assembly (and the FRPP clutch line)..

Stock clutch (for now) until I win the lottery and/or my warranty expires.

 

[VoodooBoss]

Are we talking about Ford Racing part # M-7512-A?
Edit: I just got off the phone with Ford Racing Technical support, who agreed the FR clutch line was a heat protection device, rather than an expansion control or fluid capacity device.

Yep. The clutch line does nothing to fix clutch/shifting issues. Several of us were told this directly from a Ford Racing engineer who has intimate knowledge of the Bosses.

With these items, as well as the efforts of people to address this issue as background, the following questions occur to me:

• Why does Rick's Mcleod clutch still have pedal issues with the assist spring in, while Justin's Centerforce does not? Is there some fundamental difference between the 2 clutch assemblies that one could point to as the cause for this?

As I found out the clutch sticking to the floor has nothing to do with shifting lock out. The clutch sticking is related to the hydraulic system and TO bearing. Removing the spring does fix the issue but as I've mentioned before IMO it's a band aid fix and not solving the problem. I was having my pedal stick to the floor at a track and at lunch time removed the spring. The pedal has not stuck to the floor since then. Not once not even close.

The shifting lock out is related to the clutch not fully releasing at high RPM's possibly due to the centrifugal force of the large clutch plate and weak springs not being able to overcome that force. I have missed a lot of shifts especially from 2-3 at Sonoma and Laguna Seca. After installing my McLeod RXT clutch I have not missed a single shift.

BTW great post!

 

[VoodooBoss]

I didnt like how the clutch felt with the spring removed with the factory clutch. with the centerforce and the spring removed its nearly identical to the stock clutch with the spring in amount of force to push the clutch in and just feels silky smooth.

I am a firm believer that the spring isnt helping the poorly designed clutch and the clutch needs to be replaced regardless. I would look to maybe a centerforce dual friction single disc clutch if you are on a budget but no promises that it will work as I havent tried that clutch in this car only previous mustangs.

Yours and other members comments about how the clutch felt after removing the spring kept me from doing this. But I knew I could try it as a last resort and it worked. I never felt the stock clutch with the spring removed but it feels fine with the McLeod. Much to my surprise my twin disc clutch had a lighter feel than stock. I think the key to the clutch replacement is using the smaller plate twin disc clutches that keeps the centrifugal force closer to the center line of the drive train.

 

[isrboss]

Okay, so I did a little studying today, and this is what I learned. As per the JHR video the OEM clutch line measures .149 at both openings this bottles down to .078 to the hose. The JHR's line smallest opening is .135 through the line. Ford racing's M-7512-A as per FR measures, braided side .203, solid side .205. This is what was released to me, take it how you will. If it was done unintentionally or not i'm not sure, but .200 is larger than .149.

 

[Justin]

Okay, so I did a little studying today, and this is what I learned. As per the JHR video the OEM clutch line measures .149 at both openings this bottles down to .078 to the hose. The JHR's line smallest opening is .135 through the line. Ford racing's M-7512-A as per FR measures, braided side .203, solid side .205. This is what was released to me, take it how you will. If it was done unintentionally or not i'm not sure, but .200 is larger than .149.

I dont think it will make a difference. certianly wouldnt spend 200+ for .06 larger opening. only reason I kept my JHR is because I planned to get headers at some point.

 

[isrboss]

I dont think it will make a difference. certianly wouldnt spend 200+ for .06 larger opening. only reason I kept my JHR is because I planned to get headers at some point.

What was your impression of the JHR prior to Centerforce? Did it return any positives?

 

[Justin]

What was your impression of the JHR prior to Centerforce? Did it return any positives?

Made no difference. I tried everything prior to the clutch. I secretly hope the transmission lets go so the wife will let me put a T56 XL on the credit card lol

 

[athens7]

I realize I am very late to this party, and that others have probably already figured all of this out (except Ford, apparently). That said, I have spent the last few days researching clutch theory and talking with mechanics about this issue.

Here is a good primer on clutch theory:
http://worldtracker.org/media/library/College%20Books/Manual%20Drivetrains%20and%20Axles/Chapter04.pdf
There is an article in this month's Grassroots Motorsports magazine about the various clutch products currently available, including the Centerforce DYAD, that talks a little about the various compromises that exist in clutch design.

Clutch design is a series of compromises between conflicting needs: high torque capacity (clamping load), heat management, durability, smooth engagement, & light pedal pressure. Increases in one area lead to reductions in others, so it's a balancing act. Increased torque capability means a stronger pressure plate spring, which increases pedal effort. More aggressive friction disk surfaces yield better torque capacity and heat management, but at the cost of chattering clutchengagement.

Looking at basic clutch design, the default position for a clutch is engaged, that is, the clutch disc is clamped to the flywheel and the clutch pedal is firmly at the top of its travel. All natural force in the system is designed to create this condition. In order to disengage the clutch, greater force must be applied in the opposite direction. This is applied by the clutch pedal and linkage, in our case using a hydraulic mechanism. With this in mind, as soon as the clutch pedal is released, all forces should act to return the clutch to the top of its' travel. So why isn't this happening with our cars in high RPM environments?

The forces that act to keep the clutch engaged and the pedal up are the pressure plate diaphragm spring and the clutch pedal return springs. The forces used to disengage the clutch are the hydraulic system pistons and the clutch assist spring. As far as I can determine, these are the only forces at work. The throwout bearing does not produce any force, it merely applies linkage generated force to the diaphragm spring in order to disengage the clutch, and applies diaphragm spring force in order to push the clutch pedal back to the top of its' travel (the diaphragm spring acts as the throwout bearing return spring). The throwout bearing has no springs of its' own to contribute incremental force in either direction, so I believe we can remove it from consideration as a cause of the sticking clutch problem. The hydraulic system only applies significant force in one direction, which is to disengage the clutch. If the two piston bores are the same, applied pressure is constant from one end of the linkage to the other. If one cylinder bore is larger than the other, the smaller cylinder applies more force, and the larger cylinder moves less distance. Since the force needed to disengage the clutch disk must be greater than the spring strength of the diaphragm, it follows that the diaphragm must exert less return pressure through the hydraulic system than the clutch pedal can apply. Accordingly, I think the hydraulic system is not the most likely place to look for a solution.

If we eliminate the throwout bearing and the hydraulic system as significant generators of force to engage and disengage the clutch, we are left with the pressure plate and the mechanical parts of the clutch linkage (the return spring and the assist spring). Diaphragm type pressure plate springs have certain characteristics that are relevant here. First, because of their curved design, it takes more force to start compressing the diaphragm fingers than it takes to finish compressing them, or less pedal effort at the bottom of the clutch pedal's arc. This would imply that there is less ability for the diaphragm spring to push the pedal back up at the bottom than there is at the top. Second, if the diaphragm spring fingers are pushed beyond the level plane (concave, rather than convex) by the throwout bearing, centrifugal force will cause the fingers to want to depress further, rather than return to their convex shape. This will reduce return pressure on the clutch pedal assembly. As to the return and assist springs, a visual inspection will show that the assist spring is far stronger than the return spring, so the assist spring will control. Further, the assist spring by design actually pulls the clutch pedal up in the top half of pedal travel and down in the bottom half, creating resistance in the first part of pedal return. Interestingly, the clutch assist spring seems to be normally designed for a rod and lever clutch linkage, which makes sense, since force application would be equal in both directions due to the solid linkage. With the hydraulic linkage being unequal in force application, it stands to reason that the assist spring force would be harder to overcome on pedal return than on pedal application.

I believe both the assist spring and the pressure plate are the cause of the sticking clutch pedal problem. In their attempt to keep pedal pressures low, Ford engineers used the assist spring. As far as I can tell, the Boss specific clutch is not a completely different unit than the standard GT clutch assembly, but only a different friction disk, used to provide higher heat tolerance and improve performance. Accordingly, the diaphragm spring is likely the same as in the Mustang GT. Ford acknowledges in TSB 10-19-4 that centrifugal force acting on the diaphragm fingers can cause clutch pedal release issues. The combination of a too weak or poorly designed (straight fingers instead of the bent fingers that resist centrifugal force) diaphragm spring and the pedal return resistance created by the assist spring lead to the sticking clutch pedal. It is reasonable to assume that since the assist spring seems to generate more resistance than the diaphragm spring, this condition could worsen over time as the springs fatigue.

So, what can be done? It seems that removing the assist spring eliminates the problem, but at the cost of significantly increased pedal effort. Another approach would be a stronger pressure plate diaphragm spring, but I am not aware of one being available as a stand alone part, and it would also cause an increase in pedal effort. A complete new clutch assembly alone does not appear to solve the problem, due to the strength of the assist spring (at least in Rick's case with the RXT). The best fix available at this time seems to be the new clutch/return spring removal combination, but that is an expensive route to take, and involves potential Ford warranty issues.

Since the assist spring is so easy to remove and replace, why not pop the spring out before a track day, then pop it back in for street use? As the clutch problem is not common in ordinary driving, this could solve the problem and has the benefit of being free.

*Has anyone removed the assist spring and continued to have the clutch sticking problem?

My dealership friend spoke with a Ford engineer yesterday. The engineer unofficially acknowledged that Ford has received many complaints about this problem and "is investigating". He admitted that the new GT500s with the assist spring pedal assembly are also suffering the clutch pedal problem. That makes 2 groups of high dollar Mustang owners with this concern; fortunately, since the GT500 is still in production, our issue may get some attention. To me, the question is whether Ford can build a pressure plate assembly strong enough to overcome the assist spring resistance without incurring too much pedal effort? I don't think they can eliminate the assist spring, based on the complaints heard from the automotive press about clutch effort when the 2013 GT500 came out. I also doubt Ford will spend the money necessary to put a dual plate clutch in the car, not to mention having to deal with the possibility of clutch chatter inherent in dual plate clutches (compromises, always compromises).

One other tidbit from the Ford engineer: He suggested using DOT 5.1 brake fluid. Apparently, it may be more viscous than DOT 3 or 4 and could provide a little more return force. He was not willing to go on record in any way, however.

 

[athens7]

A couple of questions:

• Justin, did you ever have both the Centerforce clutch and the assist spring installed in your car at the same time? If so, did you have any sticking clutch problems?
• Has anyone had a sticking clutch after removing the assist spring?
• Has anyone seen the pressure plate diaphragm spring from a stock Boss clutch? Are the fingers straight or bent?
• Can anyone confirm the exact differences between a Boss clutch and a GT (not GT500) clutch?

 

[Justin]

A couple of questions:

• Justin, did you ever have both the Centerforce clutch and the assist spring installed in your car at the same time? If so, did you have any sticking clutch problems?
• Has anyone had a sticking clutch after removing the assist spring?
• Has anyone seen the pressure plate diaphragm spring from a stock Boss clutch? Are the fingers straight or bent?
• Can anyone confirm the exact differences between a Boss clutch and a GT (not GT500) clutch?

i did have both. Didn't stick to floor even at 8200 rpm shifts. Just didn't like the feeling of where the spring transitioned it was right at the engagement point making for less then ideal low speed starts. Now that its out its so much better.

I have the stock clutch sitting in a box in the garage. Everything on it looks fine to me.

 

[athens7]

I have the stock clutch sitting in a box in the garage. Everything on it looks fine to me.

Sorry, Justin, I was not being clear. Bent diaphragm fingers refers to a style of finger that has a bent angle built into it, rather than being straight along it's entire length. The purpose of the bent finger is to prevent centrifugal force from causing release problems (like ours). The Centerforce has bent fingers. Could you post a picture of the diaphragm fingers?

Btw, I spoke with Centerforce, and they say their Mustang 5.0 DYAD clutch is for the 2011 Mustang. They don't say it won't work in the Boss, just that they don't know if it will fit. How did you determine it was a good match?

 

[VoodooBoss]

Brad, great post with a lot of good information. Everyone needs to keep in mind that the clutch pedal sticking and shifting lockout issues are not related. The pedal sticking to the floor is related to the spring and some mechanical aspects of the clutch operation. This is evidenced by the clutch being fully engaged with the pedal stuck to the floor and not disengaged. The high RPM shifting lockout is caused from the clutch not fully releasing. You don't need do disengage the clutch to get it out of gear at high RPM's but you will to get it back into gear. From my perspective and experience removing the assist spring does fix the pedal sticking to the floor and replacing the stock clutch with a smaller diameter twin disc clutch fixes the shifting lockout. AFAIK nobody has had the clutch stick after removing the assist spring.

BTW the stock clutch does have bent fingers and this is my clutch below.