How to prolong the life of your clutch
 

Let me be the first to say that this isn’t for everyone and that we don’t completely understand everything about clutches.

However, what is stated here will help extend the life of the clutch by keeping the clutch cooler and the fluid cleaner for much longer than any other method. This is primarily meant for those of us with stock clutches but will apply to all the aftermarket clutches as well. We have heard of many people that have put clutches in their vehicle when it may not have been necessary or many feel it is a mandatory upgrade with more power.

On our shop car we have a heads and cam C6 z06 with 585RWHP and 535RWTQ and 82K miles STOCK clutch from new and the car is driven like it is stolen, daily. The car has some drag racing time on it at the track but it is mostly thrashed on the street and road coursed as much as time and the budget allow. We have NEVER had the pedal stick to the floor and it takes about 5K miles for the fluid to change color let alone turn dark.

Drag racing does play havoc on a clutch but hopefully this will get those that are apprehensive out there to beat the tar out of their cars like they should be, it’s good for them!! It has been our experience that the 2 worst GM V8 vehicles out there for having issues with clutches are the GTO and the F-bodies. I would like to point out one thing that they have in common: They do not have an "exhaust" for clutch debris and heat. The back of the bell housing does not have vents like the Corvette and especially the C6. The 2 C6 vents are about 2" by 3/4" just beneath the clutch and in the back of the bell housing whereas the C5 was about 1/3 the size. The late model Camaro has a large vent roughly equivalent to the C6 size.

I mention all of this as an important backdrop that we will come back to shortly and I will try to tie it all together.

Even though this is a LONG write up IN SHORT it will only help even if you aren't have any issues.

I tried to illustrate with my kindergarten drawing ability ;) Check out the clutch airflow pic at the bottom.

-Bleed the clutch line
Many of us are familiar with Ranger's articles about using a turkey baster to draw out dirty fluid and then replenish with clean the fluid.

This helps, however it is not the solution for the larger issue, you will still continue to get filth in the clutch and reservoir.

Please understand I am extremely grateful for his contributions to the corvette community. Ranger sent the fluid to a lab to analyze what the dark substance was in the fluid and established that it was clutch material. Without this important piece of info we would have much less knowledge about this system. THANK YOU RANGER!!

As you USE the clutch you consume it and where does the debris go? As the clutch material is flung around within the bell housing the material gets past a seal into the slave cylinder and then the hydraulic system the fluid is contaminated and begins to darken. If allowed to worsen you eventually will have a sticking pedal and lose hydraulics. In most cases not permanent but often at the most inopportune times. It is best to address this as early as possible so you do not have permanent issues with the stock slave.

We are not sure but it seems likely that damage may be caused to the slave cylinder by the clutch particles embedding between the bore and piston of the slave. Catch it before its too late. Naturally a clutch should give off the most debris upon break-in.

The factory system moves a very small amount of fluid in a line from the reservoir to the slave, fore and aft. Naturally the most contaminants would be at the point of entry into the system, not just the reservoir two feet away. Bleeding the system like a brake or any other hydraulic system until the fluid is clear would rejuvenate and minimalize the contaminants.

A remote bleeder is nice and convenient but not all of us are willing or able to put a remote bleeder in or quite honestly I don’t know if you can even get one installed without tearing the torque tube and clutch out. So what can we do that is not too labor intensive and wont cost much? or How can we optimize this system and make it last? Whether its the basic STOCK clutch setup or a rather expensive aftermarket clutch this should only help. We are going to tell you how we do it in the car without too much labor.

The easiest way that we have found is to pull the intake manifold for the C5 and C6 Corvettes. We have ported hundreds of manifolds so we have become proficient at pulling intake manifolds. (Total time to clean head ports and put it back on about 45min.) This will allow one to lay in and across the engine bay. With your head right at the firewall with a 9mm combination wrench and a light just barely have enough room to see the port, pop off the rubber cap (leave it off) and open it while someone else is depressing the clutch pedal. Bleed it just like a brake system, one person (A) holds pedal, the other (B) opens the port till fluid pours out and then closes, (A) pumps pedal till firm again and then repeat till fluid is clear, 3-12 cycles. Remember to check the reservoir! Refill it so you do not get any air in the line. Earlier F bodies and GTOs may be accessible from under the car and may not require pulling the intake manifold.

-Open front of the bell housing by removing the plastic panels
There are 2 black plastic panels that cover the front side of the bell housing. The driver side has a small 3” panel held in place by 1-10mm bolt. The passenger side panel surrounds where the starter engages the flywheel. Disconnect battery, remove the 2- 15mm bolts and push the starter forward enough to pull out plastic panel. Before you reinstall the starter you can benefit from this wide open space. Check out the next step, Compressed air.

Total time will be between 10min and 1hr depending on stock exhaust manifold or headers and adjoining piping and space restraints and if on a lift or on the ground.

I would imagine that the panels were put in there to keep things from getting into the bell housing but the irony could be what was meant to protect the clutch hurt the longevity of it. The Driver side is shielded by the oil filter and the starter on the passenger side. It is quite amazing the amount of air moved by the clutch at idle from the “exhaust” ports of the bell housing, imagine what it would be in CFM@155mph 7k rpm. Ever heard of Smokey Yunicks flywheel supercharger?

Opening the front side of the bell housing is a crucial part of keeping things cleaner and cooler within the clutch. By allowing the front side of the bell housing to ingest airflow we now have a cross flow of air coming in and out of the bell housing and the faster we go the more volume of air through, like a radiator. With greater volume of high velocity air the clutch debris is expelled much more quickly rather than staying in the bell housing longer like the stock stagnant closed-front-entry (or it doesn’t exit but through a tiny hole like earlier Fbodies and GTOs). On our C6Z we even “ported” the “exhaust” side of the bell housing to even more aid in getting the airflow out. Futhermore, after about 7K miles we again cleaned it there was very little debris in the clutch and bell housing area and the fluid was in great shape too.
We feel that this is conclusive that it does keep the clutch much cleaner and cooler. What happens to a radiator when you block its airflow?

One more thing to mention about the GTOs and Fbodies: It has been our experience that the Heat and the clutch debris can very quickly ruin your fun. A few years back we had an ‘05 80K mile GTO with about 390RWHP and boltons, stock clutch. The vehicle was at a road course event and as the vehicle heated up it would lose hydraulics and not even be able to execute a gear shift by the end of a lap. We would have to draw out the DIRTY fluid and replace it every lap. (It is unknown how large a role the heat played it is difficult to test independently. When both sides of the bell housing are open it seems that it is no longer an issue.) Now looking back upon those experiences I know we could have resolved or at least greatly extended the proper functioning of the clutch. Since GTOs and earlier Fbodies do not have “exhausts” on their bell housings I would like to machine a few passages in there and see what happens......Now we have done the aforementioned methods to said vehicles and it has helped rather significantly but they NEED is the “exhaust” side opened up. When you take a look at the bigger picture you can see that it needs both clean high speed air in and high speed air out, just like an engine. Having only one side of it is merely half the battle.

-Use Compressed air and brake clean to blow out bell housing
Now that the panels are off you can get in there with a compressed air probe and blow out all the crevices of the clutch. We have been in there for over 10 minutes still finding more areas that blow out clouds or clutch debris. When you think you’ve blown it out enough keeping going. Then rotate the motor over with a breaker bar and do it again till there is no more clutch debris coming out. Next take 2-3 cans of brake clean and spray it all through anywhere you can. Wear a respirator and have some fans going in a well ventilated area, this is not good stuff to breathe in. Reassemble it and go beat the piss out of it.

We have a customer with a 30K mi 600RWHP C6Z that began to have some clutch slippage. We opened up the front side blew out and cleaned out the bell housing and has yet to have the problem again. One thing to consider is the contact surface of the disc and flywheel. If there is a boatload of dust in there, the surface has been compromised. The grip integrity of a clean surface has changed. Now it doesn't lay all the dust out evenly either so there is a even better chance that you will develop hot spots on the flywheel if one area slips on its own dust and another area grabs. Slowly we began to see how one thing leans on another, heat and dust ,dust and heat.

-Clutch stop and removal of the clutch spring
At the PRI show 2010 we spoke with a few clutch engineers about clutch stops for limiting travel and extending the life of any clutch by not over extending the springs in the pressure plate. From what we gleaned the more you extend a spring past a given point time and time again you will diminish its strength. The Ideal is to only depress the pedal to what is necessary for engagement and disengagement, anything more is wasted energy. What we want to do is reduce its travel by about 20-33%. If we limit the pedal travel by say 25% on the engagement and disengagement we can also reduce the shift times by a small amount.

We made our own clutch stop from: a freeze plug with a bolt with its head welded to the center of the concave side, 2 nuts and 2 lock washers. With the convex side contacting the clutch switch and the threaded side toward your foot (The C5 and C6 have a pad that contacts the clutch switch (until ’09) on the pedal that you can drill a place to set the spacing by adjusting the threaded portion of the bolt and jam nuts. There is a thread here somewhere on CF about that.

-Change the Fluid to a higher heat rating
We feel this is the least important but it is a factor. We went to MOTUL RBF 600 instead of the typical DOT3 as another measure to address what we felt could be part of the problem. We didn’t measure the temps within the bell housing but by running a very high boiling point fluid we felt that it was a good insurance to keep from having the clutch version of “brake fade”. With the temps encountered on a road course: coolant, trans, air temp, oil, brakes, etc. Wide open throttle and braking then upshifting and downshifting for half an hour non stop. There is no other way to simulate these on the street. This was our test bed as well as the street. It has held up much better than we have anticipated.

Well this research has been going on for a few years now and still learning everyday. Hopefully it didn't take you a year to read all of this ;)
Often we are very busy so please be patient as I may only get back to this thread about once a week. Thank you all for reading and I hope that it is helpful to the LS community.

Jeremy Formato of FASTERPROMS

Great info, great read and should be a sticky. Clutches in a corvette are a PIA to change out. Everything we can do to prolong our investment of costly stock or aftermarket clutches is always important and value gained. Kudo's on the bitchin write up. I follow just about everything in this write over the last 4years and have so many less clutch woes as i used to.
:flag:
:)

Good stuff.....:thumbs:

Very informative post, thank you :thumbs:

I will remove the plastic panels next time I have access to a lift.

Great post, Jeremy.

To anybody who has removed the plastic parts already...

Have you noticed any negative side to this? Any new noises in the clutch from road debris or change in clutch performance in wet conditions?

I entertained the idea of removing these pieces during my clutch swap but fear that grease, oil, sand and dirt could easily get into the clutch assembly and create havoc. Other things include a marble of tire from the track... it would stink to high heaven if it heated up and melted in there.

I'm not shooting down the idea (because I had the same thoughts last year), just looking for any data others may have. Maybe some sort of screen would be the best answer for this in place of the plastic pieces.

My $0.02

Sean

Edit: maybe one could remove the plastic pieces, drill a series of small (1/8") holes and reinstall. It would protect from large debris and still allow the bell housing to breathe better.

:iagree: You are reading my mind ........ overall I think the idea has merit , certainly makes sense from an air flow perspective. The challenge will be to let as much air through as possible while keeping all other FOD [ foreign object debris ] out. :thumbs: to the OP for another great idea shared on this forum. :cheers:

Jeremy, thanks for taking the time for the post. I think you are right on point with this information and I think I can demonstrate it with video.

First of all, for those that don't follow my travails, I currently have 462 drag strip launches and 61,859 daily driving (stop and go I-95) miles on my original equipment clutch. I have been doing the Ranger method since the car was brand new, always before, and after a drag strip event (which are at least monthly, sometimes more). The clutch pedal started sticking to the floor after I put in a cam, once I took out the pedal spring it has never stuck since.

So I think I'm qualified to comment in this thread on stock clutches.

I see trails of clutch dust on the exhaust ports that you see in Jeremy's pictures.

I think the key to my longevity is my religious Ranger method of cleaning the clutch fluid. It never gets that dirty, just a little dirty, before cleanings.


Check out my launches in these videos...you can actually see the clutch dust coming out of the car. So I think you are right on point, and your solution here has real merit.

I think I'm going to pull the inspection plates up front and see what's going on!

BTW it's not lost on me that Jeremy is a vendor here and is not selling anything in this thread - just providing the community the benefit of his knowledge and R&D for free. Hats off to that.:cheers:

Anyone have an pics of the location of the 2-15mm bolts the OP is referring to? I am trying to figure this whole process out (not a mechanic) a pics are great. :cheers:

Stock clutch gets 2 1.44's within 4 minutes
 

Hey Jeremy,

Here's more support for keeping the clutch fluid clean.

Went to the track yesterday, I ran 4 times, two 1.44 60 foots in a row though I missed 3rd the first time. This run below was a hot lap and an identical 1.44 60. I launched at 6746 rpm and the track held twice. Stock OE clutch, 61,869 miles and 466 drag strip runs, I didn't go back for a 10.7 slip.

Here's the video, check out the dust on this launch.:

Roc out- the 15mm are the bolts holding in the starter. 1 10mm holds each side panel to the OIL pan.
Joe G -Thank you sir. This method should greatly decrease the frequency necessary cleanings (in the neighborhood of a few thousand miles, rather than a few hundred) as well as keep things cooler.
Taken and REVAK- While its certainly possible to get something VERY small in there it is extremely remote. I have 11 track events on there and about 13K miles and no issue EVER, not in torrential downpours not in sand or rocks. The clearance is rather tight in between the teeth of the flywheel and the bell housing about 1/4" around the outer circumference. Also the oil filter shrouds the driver side and the starter on the passenger side. So of the total area exposed only a tiny bit of that outer circumference it could enter and only about 1/4" around the edge. I would get under the vehicle look at it and then get it fired up and just see what it does at idle speed in terms of how fast its moving then imagine what its doing at high RPM. So in summation I do not feel that there is anything larger than a pebble that COULD get in there but it would have to curve around either the starter or the oil filter. Then if it did it would most likely hit the flywheel and bounce off , because of the larger exposed area spinning at high speed and not in the line of ingestion. BUT IF IT DID get past that it would hit the teeth and get ground up and spit out in less than a second. I personally do not fell any threat of debris causing any damage whatsoever. However if you do modify what I have stated with a screen and it should work well.
Thank you
Jeremy

Great post Jeremy, thanks for taking the time to write everything out.

I pulled the plastic covers on my car right after you and I spoke about it a few months ago.

I do the Ranger method before and after, as Joe mentioned, as long as I've had the car.

Before the plastic cover removal, it would take 3-4 cycles of a full reservoir to get the clutch fluid back to clear after a track event. Now that I removed the covers, the fluid is barely tinted and only takes 1 or at the very most 2 cycles to get back to clear.

I do need to get in there with compressed air and brake clean to get all the crud out, but for now, it's holding up just fine. Maybe I'll give you guys a call and see if I can't have you do that and the clutch pedal stop mod.

Thanks :thumbs:

I will take it apart next time I have my car on ramps and check things out. :D

Jeremy did this for me when he put in my Ported Intake and TB and the clutch is much more firm and responsive.

Jeremy, thanks for the feedback. It's comforting to know that you had plenty of data with this mod. I may give it a try before my next track event in a couple weeks even though I have never had an issue with my clutch on the road course (drag strip is another story).

Once again, great idea!

Thanks for the follow up Jeremy, I am going to do this at my next oil change. :thumbs:

Fascinating. Don't have a manual so doesn't apply to me but found it interesting.....and makes sense to me. Thanks for sharing. :thumbs:

Gang,

Thank you! Good read - I have been planning to go ahead and change my C5's fluid. I wont be doing it myself so what should I expect this to cost? 1hr labor plus new fluid at a cost of how much? Is it more than an hour labor or are there any other costs to add in?

1 hour? Ha, that's a good one...

All joking aside, you hold expect 8-10 hrs if labor. While you are in there you may want to consider a new slave cylinder and a remote clutch bleed.

Maybe I was unclear. I didn't mean having all the work done as described above in this thread and the related threads, I merely meant replacing the used, dirty and chunky fluid with fresh fluid. I want to do the rest of the work but I have to wait for $$ to become available, so for now I am just going to do the fluid change.

In the properly equipped shop this can't be more than a 60-90 min job, right? Am I missing something fundamental?

So, what would you expect the cost to be to have a hydraulic fluid change done at a shop?