Clutch Slippage

1) Is it even possible to install the disc backwards? I seem to remember there was a very shallow recess in the flywheel that would not allow you to do so.(unless you like sledge hammers and crowbars!) 2) Its a 3 fingered plate. I'm pretty sure the t.o. had a flat face. 3)I have the stock bushing, not a bearing. I did add some lube, but was it too much? Wouldnt it eventually burn off? 4) By gap, do you mean between the disc and pressure plate? Explain this a little more please. If Im following you correctly then there should be no gap when the pedal is not depressed, correct? This way I can tell if the clutch is constantly engaged or if something is actually slipping. If it is on all the time then I have a clearance/adjustment problem. If is slipping, then I need parts!

MarlinJack, this at least gives me a direction in which to go instead of just throwing parts at it. Thats not my idea of a good mechanic. The weekend is almost upon us. I will report back afterwards.Thanks.

quote:

The T.O. Bearings are different for each. i.e. The 3-Fingered Plate takes a 'Flat' Faced T.O. Bearing and the Diaphram Plate requires the 'Convex' Faced Bearing.

HMMMMM, I didn't know this. I converted from a diaphram style to a 3 finger and didn't change the bearing. Would this cause slippage or a problem with disengagement?
Will

I too have a clutch slippage problem. I just bought my 1985 GT5 that is pretty much in full race tune. The car was only driven a few miles last year. When I took my first spin I discovered two things. 1.)The car is scary fast. 2)The car is scary fast even with the clutch slipping at higher RPMs. I read up on the free play adjustment. My adjustment is almost all the way against the stop. Which to me looks like this would make the clutch disengagement at max. Also I disconnected the clevis pin, and the plunger traveled past clevis point toward the rear of car. I am having no troubles shifting into any gear, including reverse, and the clutch starts to release at mid way point. It does not feel like I have much free pedal play. I am not the best mechanic. Any thoughts? Oh yeah, I love my new Pantera slippery clutch and all.

Larry

Is there some play in the pedal before you feel pressure?
Is there some movement (you may need to use vice grips or channel pliars)in the clutch lever? There needs to be or else the clutch disk may not be getting full pressure
BTW, lets see some pics of the car.
Will

There has been some talk lately that the new pressure plates are not flat. If this was a "rebuilt clutch" this is certainly something to consider.
Also as a rebuild, that means the clutch cover (pressure plate) was apart and then reassembled.

As with Chevys, these engines are now old enough to be third, forth and fifth generation aftermarket clutches. The retailers mix parts just like Chevy hot rodders do. I personally don't see that as a good thing.

If you are using a special unit like the Centerforce dual friction, the nature of the disc linings is going to permit them to slip until they are "fully broken in". Centerforce says that is a MINIMUM of 500 miles.

It is considered capable of holding 800hp. But that is fully broken in.

It's kind of like using full race brake pads on the street. Those things will feel like the brakes are hard as bricks and they are under water as far as braking ability until they are red hot. In other words they are slipping, just like the Centerforce lining is.

I can personally tell you that the Centerforce will slip more on the steel flywheel then the iron one. Also. If you installed a new aluminum flywheel, those things, depending on who's it was, probably need to be cut new, out of the box, to make them flat.

If it is some other kind of a "Spec III" puck design disc, then good luck on that one. I'm not even sure how you make that one work in a Pantera at all. Particularly considering the possibilities of mixing components here such as the disc with or without Marcel. The iron, steel or aluminum flywheel, and the lack of travel on the slave cylinder.

Best to stay with a special Pantera ONLY clutch assembly and leave the clucth "experts" go play with their Camaros, Mustangs or themselves.

As far as the throwout bearing being machined concave, that's the first I've heard of that one, but that will not make any significant differences. Don't even look there.

The 40 thousands minimum clearance is actually a little tight. 50 would be better. That usually would have shown up already in a transmission that is grinding between gears and is difficult to push the lever into gear (particularly second) without grinding.
40 may be all that you can get with the Pantera design. 50 really as I recall is unobtainium in a Pantera even with the so called "long travel" slave cylinder.

Remember also that the original Pantera clutch disc has no Marcel in it. It IS NOT the same as a CJ Mustang. But that has to do with giving the slave cylinder more travel.

My bet is that this is not a fully broken in clutch and that there isn't anything wrong with that at all.

Put at least 1,500 miles on it and see if it gets better.

quote:

the nature of the disc linings is going to permit them to slip until they are "fully broken in

Exactly. I had my original (had the De Tomaso 'Isis" logo on it) pressure plate and clutch rebuilt. Had a bit of chatter for the first few weeks. Totally gone now.

quote:

As far as the throwout bearing being machined concave

Marlin said convex, and he is correct about this. Clutch will still work with the OEM flat face, but the convex is the best choice.

I agree,since the car apparently was not driven often, you as new owner need to put on some miles and see if break-in is the real clutch issue.

Larry

OK. Convex. I still didn't notice it.

I've got both in the shop...somewhere. When I find them I'll put a straight edge on them.

I do know that in my SHO the Centerforce TOB nearly wore through the diaphram fingers at 8,000 miles.

The good setup with the SHO is to use a ceramic TOB.

These cars have constant contact with the fingers and are automatic/self adjusting by design. You can't change them.

Sounds a bit like the Pantera car doesn't it?

Incidentally. Drive the car easily for at least 500 miles with a new clutch. Otherwise all you are doing is putting hot spots on the flywheel that encourage slippage.

Concave, convex...BFD. Do you know the prismatic signature of hydrogen? Matters the same amount here.

quote:

Do you know the prismatic signature of hydrogen?

No, but maybe if you hum a few bars....

Is it possible for the material on the disc to dry up and become soft and create a slip? I now have put over 600 miles on the car and still no sign of the slip going away. I'm ready to yank it (the trans that is)and install a Centerforce unit, but it bugs me that this thing slips knowing its a stock original unit.

Simply put. No. But if it is "an original" replacement clutch then the lining is refered to as "organic".

Organic is more susceptible to oil contamination.

Unless there is a very obscure problem with the assembly, such as one of the lining rivets not being countersunk properly the likeliness is that there is a contamination on the lining such as oil.

In all honesty. I had a truck that was constantly leaking oil into the bell house and the clutch was soaked with oil and I couldn't make the thing slip. So in theory a contaminant will cause slippage but judging from what I have experience personally, it won't.

If this is so then by the process of elimination there must be a mechanical issue with the clutch itself.

If I recall correctly. If you mic the thickness of a new center disc it should be just about .340". When it is worn out it will mic something like .320".

The Pantera disc with no Marcel might have less loss of material to be considered worn out but I'm not absolutely sure about the number.

You could take it all apart and examine it. Maybe resurfacing the flywheel will clear up the problem?

I know from my own experience that Pantera clutch troubles usually are a result of trying to use a 10.5 or 11' Mustang clutch, and that just ain't the way to go.

Anyway, good luck with it and I guess you will eventually be an expert on a Pantera clutch. You aren't alone though. Your're where I started out.

Doug is right; most likely either the clutch friction surface is worn too thin, or the assembly is badly mis-adjusted, or something else is mechanically broken. Oil contamination from a leaking rear main seal or from a front ZF seal is most common but is not necessarily fatal. High performance motorcycle clutches run submerged in oil baths. But I recently worked on a Pantera who's clutch "slipped badly".... because the clutch bellcrank lever where the slave cylinder attaches was misadjusted in at least 3/8"! This meant the clutch was half- released at all times. With a LOT of trouble due to the pressures involved, I managed to get the bellcrank disconnected without breaking anything, and moved it THREE splines on the cross-shaft. What was left of the clutch then worked fine. So first, check your adjustments.

I'm not surprised at all Bossman. There are positively too many meat heads working on Panteras under the presumption that they are a Mustang with a custom body on them.

How many have stripped out the original header bolts not realizing that they are SAE threads with metric heads?

The clutch in this car, from stem to stern, is so specialized that they usually are the first sign that the really smart kid in the high school shop class got to work on the car.

At least I know the difference between convex and concave. I still need to see that throwout bearing though. It must be cut in minutes for me not to notice.

quote:

The clutch in this car, from stem to stern, is so specialized

Agreed.

When I took my assembly in to the local clutch shop for rebuilding, the counter man took one casual look and asked, a bit bewildered, what it was from. Once told, he said he had seen them before and thought that was what it was, but it had been quite some time.

Larry

Bosswrench, that was one of the many things I have tried. I disconnected the bellcrank and made it so there was a 90 degree angle between the bellcrank and the slave. I wanted to make sure the clutch was not constantly half released and also was told it gives a better mechanical advantage. I didnt think that was the problem anyway, since I could not get any thickness of feeler guage between the disc and pressure surfaces.
Guess I just solved my problem. Its gotta be a disc/Pressure plate/flywheel problem and not an adjustment thing. CENTERFORCE TIME!

quote:

Originally posted by firstpantera:
Bosswrench, that was one of the many things I have tried. I disconnected the bellcrank and made it so there was a 90 degree angle between the bellcrank and the slave. I wanted to make sure the clutch was not constantly half released and also was told it gives a better mechanical advantage. I didnt think that was the problem anyway, since I could not get any thickness of feeler guage between the disc and pressure surfaces.
Guess I just solved my problem. Its gotta be a disc/Pressure plate/flywheel problem and not an adjustment thing. CENTERFORCE TIME!

Just be aware that the people at Centerforce are not anyones best friend but themselves.

If you need to talk to a tech there it is gonna be Gene. Good luck with him. Been there done that...on more then several occassions. How exactly a new disc under warranty wound up costing me $100 is beyond me?

He's the type of guy that if you saw him standing in the pouring rain at midnight 100 miles from civilization with a flat tire but with no jack you would consider driving really fast through the closest puddle and aim it in his direction.

If I knew him a little better I'd calculate how far the body might travel if I hit him at 70mph. Fortunately for both of us, I don't.

Also the Centerforce for the Pantera (got it's own special part number and everything) is a 10.5" unit. Usually a 351 would use every bit of 11". It's also one of the more expensive specific clutches they make. Like $600 or $700 or something like that. At least that's what I paid Hall Pantera for it.

I can't explain exactly why the 10.5" disc works so well in the Pantera but it even seems to help with clutch travel and release. Amazing that someone actually did something right.

Also remember to use that feeler gauge in setting up the clutch. When you see it all fall together and figure it out it will seem like an epiphany.

As an aside I am told that the disc is made "off shore". Apparently there are some "no good components in the lining mixture" so try not to eat any of it?

So after all of the questions and good advice I yanked out the trans and installed the centerforce pressure plate and disc on the redrilled and refaced original flywheel. Got to drive it for the first time this Saturday and DAMN, THIS THING FLYS!!!!!
I took some measurements before I assembled everything and i had a little over 3/8" clearance between the throwout bearing and the pressure plate. I didnt check it with the orignal parts but I'm thinking that the bearing was in constant contact with the pressure plate and keeping the clutch slightly engaged causing the slippage. Is that possible?

quote:

I didnt check it with the orignal parts but I'm thinking that the bearing was in constant contact with the pressure plate and keeping the clutch slightly engaged causing the slippage. Is that possible?

Absolutely possible. And while some throwout bearings are advertised as 'constant-contact', they simply cannot have as long a life as the 'normal' type that have a little clearance in neurtal. Glad you straightened the thing out. Have fun-

In my experience it isn't the throwout bearing that has the problem with constant contact. It is the fingers on the pressure plate.

I have a Centerforce sitting here that was a specific build for my Taurus SHO. That pressure plate is a diaphram design and the fingers are worn about 1/2 way through with about 8,000 miles of useage.

The self adjusting pawl in that design keeps the throwout bearing in constant contact with the fingers.

Something was obviously wrong there and it isn't me.

What I am saying is that don't presume anything on these things. Double check everything, then double check that.

This makes me think of the CompCAm camshaft that I bought and straight out of the box the distributor drive gears on the cam were missing a couple of teeth.

They told me that the warranty didn't cover that but as a courtesy they would replace the camshaft. Bear in mind that it had not been installed or run. This is how it cam out of the package.

In further discussion with the Tech guy he told me that to cut costs CompCams didn't check each and every camshaft. At the time it was 1 in three that they checked. The blanks are not US made (Chinese) and they can only be checked by a real live person and that would raise the price of the product which is price sensitive.

The point is, the Centerforce is "assembled off-shore". Why would I presume that they would be any different on checking quality then Comp Cams.

Just a word to the wise about "after-market" parts. Buyer beware.