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Discussion Starter · #1 ·
Hi everyone! so my father and I recently installed a new diaphragm clutch in our mustang. The clutch is a Jegs street performance clutch kit. we replaced the flywheel as well which was a direct replacement. Once we got everything installed, we found the the clutch was not disengaging, and the only way to get it to disengage was to preload the throw-out bearing on the clutch springs(only for testing purposes). We found the clutch linkage needs probably an extra quarter of an inch of throw to be able to work correctly. We aren't completely sure what's causing this issue, I'm assuming it must be excess play in the z bar, but it has fresh bushings so it doesn't make a lot of sense. We are now considering installing a hydraulic clutch conversion kit, but the only options for the t4 are at least 650 dollars. I found there is a version for the t5 transmission that is about half the price. I was curious to know if a t5 kit could work with a t4? or if anyone has suggestions on the clutch issue by all means let me know! thanks!
 

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Yeah, maybe you should call Jegs and have a conversation.... assuming all of your linkage is in good shape.... including the pedal support.
 
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Discussion Starter · #3 ·
Yeah, maybe you should call Jegs and have a conversation.... assuming all of your linkage is in good shape.... including the pedal support.
I have been considering, maybe ill give it a shot. Yeah the car was restored a couple years ago and has seen very little road, so it all should be correct and in order. The big difference we noticed was that, from the previous clutch (which was a 3 finger,) the spring fingers were recessed inside of the pressure plate, where as the new diaphragms springs stick out about an inch. so we were thinking this may be throwing off the geometry.
 

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Russ, would a spacer or a different throwout give you enough room ? I think I would exhaust all avenues before even thinking of a juice clutch. Are we sure that pressure plate has the right finger height for what you are trying to do ? LSG
 

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Hi everyone! so my father and I recently installed a new diaphragm clutch in our mustang. The clutch is a Jegs street performance clutch kit. we replaced the flywheel as well which was a direct replacement. Once we got everything installed, we found the the clutch was not disengaging, and the only way to get it to disengage was to preload the throw-out bearing on the clutch springs(only for testing purposes). We found the clutch linkage needs probably an extra quarter of an inch of throw to be able to work correctly. We aren't completely sure what's causing this issue, I'm assuming it must be excess play in the z bar, but it has fresh bushings so it doesn't make a lot of sense. We are now considering installing a hydraulic clutch conversion kit, but the only options for the t4 are at least 650 dollars. I found there is a version for the t5 transmission that is about half the price. I was curious to know if a t5 kit could work with a t4? or if anyone has suggestions on the clutch issue by all means let me know! thanks!
If I am reading this right your clutch pedal stays depressed correct? All components seem to be in good working order? After your diaphragm clutch install it began to act up? If all seems to have gone together correctly I had a similar problem on one of my cars , what seems to happen on those clutches is when the clutch pedal goes over center with a diaphragm clutch you need to install a helper return spring under your dash ... Helping pull back your clutch pedal. Would this be your situation?
 

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Yeah, I wouldn't say that's an accurate assessment of what he wrote at all.....
 

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Discussion Starter · #7 ·
Russ, would a spacer or a different throwout give you enough room ? I think I would exhaust all avenues before even thinking of a juice clutch. Are we sure that pressure plate has the right finger height for what you are trying to do ? LSG
Unfortunately, the only thing a spacer or larger bearing would do, is get it closer into contact with the clutch, which we are already able to adjust for it in the linkage, the issue is, we just don't get enough "throw" out of the clutch linkage, so the bearing needs to be in semi-hard contact with the Pressure plate springs in order to fully sperate the clutch disk from the flywheel.
 

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Discussion Starter · #8 ·
If I am reading this right your clutch pedal stays depressed correct? All components seem to be in good working order? After your diaphragm clutch install it began to act up? If all seems to have gone together correctly I had a similar problem on one of my cars , what seems to happen on those clutches is when the clutch pedal goes over center with a diaphragm clutch you need to install a helper return spring under your dash ... Helping pull back your clutch pedal. Would this be your situation?
No, the pedal returns fine, the issue is that the clutch itself will not separate from the flywheel unless we bring the throw-out bearing into contact with the pressure plate springs. so it seems like we may have a good amount of loss in the z-bar linkage but we don't know for sure.
 

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I thought that late model 5.0 diaphragm clutches use a little preload on the throwout bearing...basically contacting it....(which seems counter intuitive...or prone for wear.) But that is what I remember...I could be wrong
 

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I wish I could help, but the only thing I can offer up is my setup. I'm running completely stock clutch linkage for a 69 428 car, with a 390 clutch fork, Mcleod diaphragm clutch/pressure plate setup, stock bell housing with a TKO600. It operates perfectly with no issues.

I wonder if maybe the fork isn't hooked onto the bell housing correctly.
 
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Discussion Starter · #11 ·
I wish I could help, but the only thing I can offer up is my setup. I'm running completely stock clutch linkage for a 69 428 car, with a 390 clutch fork, Mcleod diaphragm clutch/pressure plate setup, stock bell housing with a TKO600. It operates perfectly with no issues.

I wonder if maybe the fork isn't hooked onto the bell housing correctly.
funny enough, I didn't have the pivot aligned fully in the fork, but even after going in and reseating it, the issue is still there.
 

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I thought that late model 5.0 diaphragm clutches use a little preload on the throwout bearing...basically contacting it....(which seems counter intuitive...or prone for wear.) But that is what I remember...I could be wrong
I believe basically all cars that have a diaphragm clutch from the factory run with preload. On the diaphragm you are pushing on a spring, not a solid connection like the old 3 arm long clutches. A tiny amount of preload probably have nearly no impact on the clamping force.

But is looks like there may sometimes be a mismatch between the diaphragms clutches sold and the stock zbar linkages. Kelly H wrote somewhere she tried to use a new diaphragm clutch in her car, but that it made the pedal crazy stiff. I'm pretty sure she actually had the opposite problem of this thread. That she had to much move of the throwout bearing (or you could say to little ratio in the stock linkage) for that pressure plate. I have also had an Ford diaphragm clutch that felt way to stiff with my stock zbar linkage. A small change in the ratio of the linkage made the pedal feel much better.
 

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Discussion Starter · #13 ·
I believe basically all cars that have a diaphragm clutch from the factory run with preload. On the diaphragm you are pushing on a spring, not a solid connection like the old 3 arm long clutches. A tiny amount of preload probably have nearly no impact on the clamping force.

But is looks like there may sometimes be a mismatch between the diaphragms clutches sold and the stock zbar linkages. Kelly H wrote somewhere she tried to use a new diaphragm clutch in her car, but that it made the pedal crazy stiff. I'm pretty sure she actually had the opposite problem of this thread. That she had to much move of the throwout bearing (or you could say to little ratio in the stock linkage) for that pressure plate. I have also had an Ford diaphragm clutch that felt way to stiff with my stock zbar linkage. A small change in the ratio of the linkage made the pedal feel much better.
oh okay, can i ask how you changed the ratio? did you end up extending the end of the z-bar to get a little more leverage?
 

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You shouldn't have to make any change to the ratio of the z-bar, pedal, etc. The clutch you purchased from Jegs you indicated
was "direct replacement."
I don't understand the hesitation to "call out" Jegs on this by having a phone conversation with their technical personnel.

I'd get tech calls at JBA, Global West and ACDelco on stuff as minor as a missing cotter pin......

I've got a Centerforce dual friction diaphragm clutch in my '66 and it works fine.
 
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Discussion Starter · #15 ·
You shouldn't have to make any change to the ratio of the z-bar, pedal, etc. The clutch you purchased from Jegs you indicated
was "direct replacement."
I don't understand the hesitation to "call out" Jegs on this by having a phone conversation with their technical personnel.

I'd get tech calls at JBA, Global West and ACDelco on stuff as minor as a missing cotter pin......

I've got a Centerforce dual friction diaphragm clutch in my '66 and it works fine.
Yeah you are right, I'll get in contact with them right now, ill let you know what they say.
 

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I believe basically all cars that have a diaphragm clutch from the factory run with preload. On the diaphragm you are pushing on a spring, not a solid connection like the old 3 arm long clutches. A tiny amount of preload probably have nearly no impact on the clamping force.
Not familiar with this. How does that work? (no preload on clutch release bearings.... in other words I understand you're saying that the bearing is actually
touching the spinning fingers of the PP even when the clutch pedal is not being touched)
I just "retired" from a technical sales position with NTN bearing after 8 years in the field..... this is not a story that we (as a bearing manufacturer) ever relayed
to customers in the OE or aftermarket.
 
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Not familiar with this. How does that work?
How preload works? It seems like any newer factory car have some kind of self-adjusting clutch/pedal connection that use the fingers as adjusting point. Several people in this thread also says that diaphragm clutches in factory setup use preload:


If you google you can find a lot of forum threads (all kind of car brands) where people ask why the factory have designed their car to have constant running TOB.
 

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I was being factitious. I know how preload works.
Any preload on a bearing of that design (roller thrust) simply accelerates the wear on the bearing...... regardless of what Ford, GM. Subaru or whichever OE car producer says.
(Centrifugal force and grease retention are in battle and can't be discounted by whim or fancy)
Just as a general rule, the bearing manufacturer's engineers are generally much sharper then the vehicle engineers.
 

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yeah, like I said, it is counterintuitive, but that is how they run them...preloaded. I don't like it, but that is what I had to do when I converted my son's 68 to a T5. It seems like the TOB would wear out quickly....I did end up going back to the 3 finger style pressure plate.
 

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Any preload on a bearing of that design (roller thrust) simply accelerates the wear on the bearing...... regardless of what Ford, GM. Subaru or whichever OE car producer says.
I actually think I saw a text about TOBs from one of the big OEM clutch manufactures, stating that the preload in practice make it last longer. The instructions for a McLeod hyd. TOB kit also states it a constant running design, so "preload" have also spread to the performance aftermarket. Bearings seems in general to have an impressive lifespan, even when they are running 24/7, as long as no water or dirt gets inside.

But the thought with my first comment was that when you start to "mix" parts, like here using a diaphram clutch in a car born with a Long design, you may get a part that may bolt on, but not really are engineer for the exact setup. Like a lot of those power brake conversion kits where people seem to have a hard time getting the right pedal feel and action.
 
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