It seems that on nearly every clutch out there about half of them break within 2000mi. and others perform beyond expectations. A lot of people are wasting tons of $$ and time replacing these "bad clutches" without knowing what caused the failure . There has to be a failure mode somewhere! What is it: improper installation, incorrect flywheel/surfacing, driver error, hydraulic issues, etc? I'd like to think the quality of the clutches themselves is not so hit-or-miss, and there must be a few installation tricks/break-in procedures that make all the difference. Are there any clutch gurus out there that can enlighten us all?


P.S. Sorry for the rant, but I'm getting tired of reading nearly identical posts over and over with no real solution in sight.

 

Well I just read a post where a guy said he has 60+ passes on a clutch and it took a ****. He also said there are just over 2000 miles on the clutch. These people are beating the CRAP out these clutches and expecting them to last. I realize some people have bad luck, but man some of these posts I read are crazy. You just can't expect a clutch like the SPEC 3 to last through that kind of abuse.

 

I to would love to hear from an actual clutch guru. Seems that no matter what clutch manufacture and/or type of clutch,pick one out of a hat and mention it,you get multiple replys in both good and bad terms. I to can't see someone like Centerforce who has been making great clutch's for a long time to make garbage for an LS1. I also can't see SPEC making so many clutch's that take a dump in so little time as the same for the other manufacture's.

 

Well I have been having some issue's with my Spec and here's what I found out. I put atleast 600 miles city/stop and go only per there directions. Another 1,000 miles of highway. First time I got on the clutch was a roll on and shifted the car at 6,000 going into fifth. It didnt feel right. Well the tranny took a dump and while I had the tranny out I thought I would look at the clutch and plate.
To my surprise there has been some heat to the clutch and the pads closest to the center of the disc show very little wear to a point I can tell you what color they were when new. The disc is held tight between 2 piece and it should wear better than that. Well some phone calls to Spec netted me this answer. The clutch is Not broken in yet. Also per Spec this is how the clutch's wear in and "they have No Idea why the clutch's wear that way but they do". From talking with them I got this. There Quality control does not have the pads flat, we make them flat during break-in. So if you dont break them in right or your disc is off a bit you do not get full holding power until it is broken in. So after there break in period if you start launching the car and it isnt fully seated the clutch is not going to last. I feel this is why its hit or miss on some application. I can tell you from my clutch I have spots on my disc that have no wear mark from the middle of the lower rivit to the innner part of the disc, thats almost 1/4 of the pads, which in turn has added heat to the outside of the disc and flywheel. I'm nsidering my options now, With the race event that I do I cant afford to have a problem.
I feel this is why some of these clutch's last and why others do not. John

 

As long as you understand basic clutch theory and the hydraulics in these cars, it's very painfully obvious what the problem is with every brand new f-body sold with the hyd. throwout bearing.

GM has to warranty one thing or upgrade it, so they spend their $ the way they see fit. In the case of the 10 bolt rear, they didn't upgrade it. They have offered 2 basic axle designs since 1981 because they see it as not broken, so why fix it? While the 9-bolt Borg Warner rear in the third-gens was a "good" rear axle, it's no Dana 60.

The V8 f-body has continually gotten more powerful since 1986. The more power going through the drivetrain, the more trouble that 10 bolt rear has taking it.

In order to minimize the breakage of differentials & driveshafts, GM found a sneaky way to soften the blow of the clutch grabbing in an M6 car. The hydraulic line going from the master cylinder to the slave cylinder is physically necked down such that flow becomes restricted.

What this does is twofold. The release of the clutch can only happen so fast because the fluid is restricted, so the clutch gets a little extra "friction burn" as it's pulling the pressure plate off when you push the pedal. And similarly, but worse than that even, is that when the clutch applies, it can only apply so quickly becuase of again, the restriction. So even if you sidestep the pedal properly while hauling the mail, so as to get a firm shift, and the clutch (under normal circumstances) would normally apply quickly and without much friction burn at all, the clutch gets burned extra because it can't apply as hard as a proper hydraulic setup. The effect is that of a shock absorber on a mechanical clutch setup: artificially slowed clutch release & apply.

You'll hear "oooh, the LS1 is just too powerful for so and so to make a good clutch." Nonsense. There are clutch mfgrs. making reliable clutches for way bigger / more output engines than LS1s that are frying clutches. Those same mfgrs. get bad mouthed as being unable to build a clutch to go behind a 5.7 litre 350hp small block.

You'll notice that Cobras don't have this issue. Their cable release is a cable setup with no restriction. While I'm not saying that their fewer-spline input shaft is a bright idea compare to the 26 spline GM & Dodge inputs, they are snapping input shafts because of the quick grab that their clutches are able to do.

When the clutch doesn't release properly, the synchro is forced to attempt to slow down the engine to match trans. speed. This is not the intended job of the synchro nor can it do that job; it is merely supposed to slow down / speed up the gears & input shaft and disc., so that the gear & synchro sleeve are spinning the same rpm and they can mesh. When the synchro can't slow down a whole powertrain, the gear doesn't match the sleeve in rpm, and the teeth clash. It's getting late, so hopefully I worded all this on a comfortable but concise level.

This is why every single f-body should have the master to slave line drilled out, and the y-body should have the slave extension line drilled out. It's not optional, it's not something that makes me a dime. It's just what is necessary for the clutch to work properly. Then, if you want to drive along slowly, you can, and release the clutch as such. If you want to kick it up a notch, you can bang gears and the clutch will work as it should. Without the drill mod, you will get the "sunday afternoon" clutch release and apply even when you are driving as if it's "friday night at the track."

I remember the first time I learned about this and I had been thinking about clutches a lot (as I had done my first successful A4 - M5 conversion not long before.) I was reading magazines @ a store on Central across from UNM in between classes. It was in one of the Chevy magazines and they explained what the problem was, the drilling of the restrictor, and I said "by God, that's it!" And rest assured, it is.

There are a lot of "overkill" clutches out there being sold, like the Stage III from Spec which isn't as streetable as it should be. A lot of marketing has taken place, and a lot of clutches have been sold becuase of General Motors' chicanery with the functionality of their powertrain in these cars. Take it from someone who doesn't stand to profit from you when your clutch or synchro gets broken (unless you're in Phx. ) ... That's the reason. That's the problem. It's been circled. Now go drill mod your car, and do the JMD bleed method while you're at it.

-matthew

 

Very informitive Matt. This is the kind of info I was looking for. I have been going crazy reading all these horror stories. I have used Centerforce clutch's in the past on older muscle cars that have made much more tq than the basic modded LS1 and they have always done well and outheld better than other big name clutch's. Time comes when I think it's time for a better clutch in my T/A due to the stock one just won't hold and 40k on the odometer and I start thinking,ok,time for a centerforce. To my surprise all I keep reading is how they make junk for LS1's and fearing making a mistake in this clutch or any other I keep putting a new one on hold. If what you say holds true for as it does seem to make all the sense in the world, then this clutch should be every bit as good and reliable as the ones I've used in the past. Please correct me if I'm wrong but from what I'm understanding I may just order it this friday. Thanks for the imput.



Shawn

 

Centerforce clutches don't work well in the Fbod. The reason why is due to the flyweights on the pressure plate fingers...they add more clamp load at high rpm and prevent the weak hydraulic system from releasing the clutch all the way. Its not necessarily Centerforces fault, but it doesnt work well. Some have had success after removing the flyweights though.

 

Thanks for the replies, especially Matt - I agree the drill mod is definitely necessary. I always assumed that everyone was doing the drill mod if they went through the trouble/expense to upgrade the clutch-maybe I'm giving some people too much credit?

I really want to believe that if I drop $1000+ for a clutch/flywheel/hydraulics package it will definitely work if I follow all the instructions, etc. Otherwise, I'm better off going with a Z06 clutch with the intentions of replacing it every season or two. At least I'll know its breaking from abuse, not random failures.

 

I think I'll just load the gun and shoot myself in the head. Would be so much easier than worrying about buying the right clutch and how long it will last.

 

why doesnt the aftermarket design a cable style conversion to do away with the slow responding hydro clutch?

 

I wish they would but in our cars that would tbe a huge undertaking...

 

I have worked with this problem for the last few months trying ot firgure out why I couldn't shift my car at WOT with my centerforce clutch. I replaced the slave with the 01-02 upgrade, and did everything their tech people told me to try to get this thing to shift properly. They finally told me an adjustable master cylinder would fix the problem. I wasn't about to spend another $300 to get my clutch to work properly. I did some research and found that the only clutch that had this problem was the centerforce, so I talked to a couple shops that installed them that said the only way tehy remedied the problem was with the Mcloed master cylinder. I talked to a firend that works for GM and he told me that not only did GM make an upgrade slave for the 01 and up cars, they also redesigned the masters to because of a bleedback problem. They never said anything about it to the public, because it would only effect a car running the centerforce clutch right off the bat because at high rpms, the wieghts ae pushing back on the throw out bearing and the fluid is bleeding back to the master cylinder keeping you from being able to bang the next gear. THis will not happen with the stock clutch or any other clutch that doesn't use centrifical wieghts to increase the clutches clamping pressure. So I decided tro try this theory out. Instead of ordering the Mcleod Master I ordered the 01 and up GM master ad threw it on there got it bled and took it out for a drive and it never worked better. I was so happy to finally have my clutch working like it should. The reason they worked fine when replace the master with teh Mcleod unit, was because like the upgraded master from GM, It had no bleed back problem. I later found out one of the dealerships in town was requiring you to give them your VIN number because they were trying to keep track of this problem.

I called centerforce and talked to their tech guys about my findings and they agreed with my findings and are going to look a little further into it, so there should be another tech article along with the centerforce clutch for LS1 cars soon.

 

These are all good points. I think that alot of people ARE driving these clutches very hard.

My dad always taught me 'your race car is your race car, your street car is your street car'. It is VERY difficulty to have a vehicle that you drive daily that runs 11's or 10's and have a wear part like the clutch last.

When we build clutches specifically for a race vehicle, they will typically go between 75 and 125 passes between rebuilds. This is when the clutch system is optimized to provide the best launch and smoothest transition between gear changes. As this happens the clutch wears; it is doing its job properly when this occurs and other driveline parts are not broken or damaged. If you ask the more professional racers out there, I think you will find they agree.

So is it hard to believe a clutch lasts 2000 miles and 60 passes - I think not, especially if the vehicle is raced hard or is very high powered.

Another fatal mistake I see every time I go to the track - hot lapping. At Darlington last weekend I watched one f-body car make 9 passes back to back. This is extremely hard on the clutch. Clutches are cooled in pro race cars for this very reason. At a certain temperature, any friction material's Cf is going to start to drop off and this is when a failure is eminent.

Just $.02 from one clutch guy.

 

Oh my GOD!!!!!!!!!!!!!!

This man is my hero,
He wrote in this thread word for word my problem. Down to the "he changed the slave and noit the master and still had trouble w/the Centerforce".

I did what was next on his list, "changing the master to the updated 2002 camaro part".............

freakin perfect shifts. I have been frustrated for 2 years with the problem he stated.

Now I can light em up 1-2 & 2-3 shifts..

u are my hero.
I signed up for this awesome sight specifacally to say thanx to red2000z28 and everone who made some good points!!!

new ls1 tech rookie
hugger1975

 

No problem, I was only fustrated with mine for a few months, but I was determined to get it fixed. No that it shifts like it is supposed to I am very happy with the centerforce clutch. They were also happy when I called them with the solution. I think I will post this in a seperate topic for those of us with the "centerforce problem".

 

thanx again,
I have a whole new excitement about my car.
I am looking 4 excuses to go for a ride.
Always granny shifting was annoying, not using the whole power band sucked.
Now I can run her up to 6000, drop 2nd and keep going.

I just hope I still have life in the old clutch to last now that I can finally enjoy it.

No sliping at all, so I hope I am good.

take care

 

My only problem now is that in the process of trying to shift at WOT with the bad master, I ended up bending a shift fork or messing up some synchros, and now the car grinds for a second going into 6th. Oh well that can be fixed later, I don't need sixth for racing.

 

how the heck did u bend that fork?

i dont think i messed mine up.
we will see on tues, when i go to the track.

 

Having this Problem with my Spec Stage 1 Clutch. Just everyday driving the Clutch does fine.. Shifting at High RPMS the clutch will not got into second at all.. I have Upgraded to 02 Slave Cylinder, Bled it a TON.. Any help would be great.. Never had a Problem with the stock.. Glide smooth.. Any info wold be great...

 

I would guess trying to jam it in gear at the track the only time I took it and figured out that there was a problem. After that, everytime I go into 6th Grrrrrr for a little bit.