You're right. When I am in the middle of a project, I don't want to be 100% focused. Instead I would much rather field calls from 100 different guys about a possible fix for a problem they might not even have. How would you feel if that was your trans on his bench that you spent 3k to have him expertly rebuild and this is going on?

It would be nice if one person (possibly the OP) could have posted that information. But no, his response is akin to spam being thrown around everywhere.




I think you got your first ZR-1 around 2007. So how long have you known Bill?

 

For what?

 

I had Bill shorten and rebuild the shifter on my 96. Plus he supplied me with a rear tailshaft bushing and seal. I was also doing a clutch job. While I never spoke to Bill on the phone, he was very gracious in quickly answering my emails and provided much needed advice about my trans and clutch job. It was a pleasure dealing with Bill.

 

This is getting ridiculous. Can a moderator please just change the thread title to, "Glowing reviews of Bill @ ZFDoc!!" so we can all move on?

 

you think this is bad, you should see some of the stuff from his 8 other forum names. Pure gold!

 

What is this, 1962? Voicemail is one option. Heck, even in the 80s we had answering machines...

You're being ridiculous. Out of 300 views this thread has to date, I doubt those people are just running to pick up the phone to call him about clutches.

Sit and think, how many ZF C4s are out there that still survive, how many of their owners are contemplating a clutch replacement, and how many will see this thread? I still doubt this thread generates a call per day. C'mon

 

What part of "forum designed to increase community knowledge" was difficult to understand? The whole point is that if this thread actually contained what its title claimed, then well after Bill has passed on to the great ZF factory in the sky people would still be able to gain from the supposed knowledge being bragged about by the OP.

If all you and the OP intended was to try to drum up business for ZFDoc, then the thread should have been titled accordingly and been in the appropriate forum.

The whole point of living is to pass knowledge on to the next generation. If the knowledge dies with you, then what was the point?

 

Guys, maybe we can salvage this thread. The issue with all replacement pull-style replacement ZF pressure plates is that there can be uneven pressure clamping the friction surface to the flywheel. The causes are twofold, and I'm going to include quotes from Jim Jandik:

1. One issue is in the main-body casting itself: "he length of each pressure plate bolt tab. Place the legs down (same as it fits to the flywheel) on a known flat surface, then see if the plate rocks on that surface. This has been a huge issue with the Chinese mfg. pressure plates. Your pretty blue SPEC plate is in reality a Chinese made piece of ****. SPEC doesn’t make the plate or t.o. bearing in their ZF Corvette clutch kits, they source them from the same factory in China, same as every one else. Anyway, I have seen the bottom of the legs be off by .040” or more compared to each other. When you bolt the plate to the flywheel, this causes an uneven space between the steel friction ring of the plate and the clutch disc, especially where the bolt goes down through the tab. The tight spots manifest themselves as the blue hotspots you see on the steel friction surfaces. Other parts of the friction surfaces show no wear because the clutch disc isn’t even engaging those areas." It is possible to correct this fault by machining the legs that are longer to the length of the shortest leg. All the pressure plate castings these days come from one mold in China...literally. but this is a more of an issue in final machining rather than casting, as I understand it. But just keep in mind that no matter the brand on your clutch, it came from that mold, and its final machining probably all took place in that same factory or a factory down the street from there.
2. "If the diaphragm levers are not at the same point in space, uneven loading will occur. You can easily check the plate for this and you don’t have to bolt it to the flywheel. Just look at the plate where you can see the thickness of each diaphragm lever. Then rotate the plate around 360 degrees in your hands. The levers should all be level with other, like keys on a piano. That is what I’m referring to, not the length of the levers where they terminate at the center of plate and form the circle where the t.o. bearing goes." IOW, the big diaphragm spring isn't even in the pressure it applies. I do not know how universal this problem is, because I don't know if all the springs are now made in the same place or not. It's a safe bet they are all made in China. But quality control appears to be an issue. I don't think there is a way to repair this short of replacing that spring with a known good one or chucking the whole pressure plate and getting a new one.

Finally, Jim told me that "Bill Boudreau is addressing the pressure plate issues by re-machining the legs on the Chinese pressure plates. That puts them all at the same length and same standoff height to the steel friction ring." I don't know if he's selling new units after checking/correcting them, or if you have to check one yourself and send it to him. At the very least, you should check your p/p for both issues before installing it. If you have issue #1, it can be fixed. If you have issue #2, I'd probably return it.

Also, if you have an OE Valeo unit, it was made in either the US or Brazil and the quality was much higher (not a new Valeo-branded p/p, which is made in China like all the others). These days, I would check it, resurface it, and put it back in service rather than buy a new Chinese one. The friction surface can be resurfaced either with a steady hand on a d/a sander, or by disassembling the p/p and surfacing the friction plate on a machine and reassembling the unit. The legs on the casting have to be shortened by however much material was taken off the friction plate, so the d/a method is better if the friction surface isn't badly damaged (i.e., doesn't require lots of material to be removed). I believe Bill Boudreax can probably help with refurbishing an old OE p/p also.

FWIW, in 2016 my clutch had to be changed and I put a SPEC unit in. It chattered, and then I had the throwout bearing seal fail and douse the friction surfaces with grease, so I had to replace it. It showed some unevenness in the p/p casting legs (problem #1), but the diaphragm spring seemed even. I ended up replacing it with a NOS Valeo unit from GM's old Escort C4 racing program (lightened friction surface, stiffer clamping pressure) that Jim resurfaced, and that setup worked well for several years before I sold the car four months ago.

The throwout bearings are another story. Any new one also appears to be made in China, and is hot garbage. The only good ones are NOS AC Delco units that have "INA" stamped in the green seal area. They are not plentiful or cheap.

 

That's it

He told me you can send one into him or do it yourself if you have the equipment to do it right. I do not see clutches on his website for sale.

 

Great post Matt. Fantastic information. Man....you know what this makes me think? It makes me think that when it's clutch time, I'd buy a new disk, grease my TOB with a grease needle, 3m/whiz wheel the PP and FW surfaces and put it back together.

It seems like that is actually a legitimate option. Why am I throwing away a know good, PP/spring assy that works just to buy questionable chinesium?

Why aren't "we" having problems like these, sourcing other clutches for other vehicles?

 

I agree. I've never tried the grease needle trick, but if I had an original INA bearing in my car I'd be inclined to try that instead of replacing it. And as you saw, I did do that with my pressure plate (well, Jim did it for me, basically).

It has to a be a numbers thing. Compared to all the millions of standard-issue push-style GM applications out there, there just isn't a big market for replacement C4 ZF clutches. And there isn't a big racing scene where aftermarket ZF clutch kits are required, either. So there's no business case for having multiple factories making them. There used to be a time, 10-15 years ago, when a SPEC clutch was a legit US or Brazilian Valeo pressure plate. I assume that was the case for other brands, too, since there was only one mold back then as well (but it wasn't in China). Those days are gone, and nobody outside of China is spending the money to make a new mold for a teeny market like ours.

 

Jim hates SPEC.

Remember that with any advice you hear about him from here.

he is salty bc their pressure plate /flywheel
balanced combos sometimes are ‘off’.

That maybe true, but the workaround is having your machine shop check it before you install it.

 

Jim couldnt grasp the power I was making on my supercharged 93, and kept trying to steer me into a puck type stage 3 clutch from carolina clutch. This clutch is known to have bad street manners.

He then refused to sell me any parts when i didnt take this suggestion

His hated SPEC, makes a product that works very well in my application. The stage 3+

i use the pretty blue SPEC chinese pressure plAte. It works fine. I checked it over for all these issues. It didnt have them.

the only real problem it had was it required a lot of drilling to neutral balance it to my aluminum flywheel.

however, i always get them balanced.

ive been thru a couple SPEC kits over the yrs and , the pretty blue flywheel didnt take much drilling (to balance) when it was the valeo model.

one spec kit i bought in 2006 included a sloppy china throwout bearing for the big guide tube (zf black tag).

however the 2012 kit i bought included a beautifully machined throwout bearing different than the crimped/stamped OEM style . It appeared to be cnc’d and machined (tree ring marks) . It was very solid.
i cant remember if i used that though !

but what im saying is dont throw the baby out with the bath water bc a loud mouthed guy had an issue with a different problem from a company

(in this case im talking jim vs SPEC)

 

Oops, I actually meant to edit that part out before pasting it in here. Too late now, I guess. But regardless, what he wrote isn't wrong: SPEC and every other clutch name out there sources its pressure plates from the same place. They like to claim they don't, but that's a lie. And the problem with uneven legs on the p/p that he was referring to in that quote actually was a problem with mine. The other problem was that the TOB was garbage and spewed grease all over my friction surfaces, requiring another teardown and clutch replacement. That's probably not unique to SPEC either, but I certainly didn't have a good experience with them.

 

Its been forever ago since I did a clutch in my 97 Camaro... But if I recall it is similar to the ZF. Wonder if the height is the same and then the next question is the clamping force. I know the actual clutch disc is the same size. Might be worth a comparison as the F-body scene is still pretty strong.

 

I agree^^^....but had assumed that this "must have been looked at" a million times by now. BUT....I've never looked at it. I'd think tq capacity would be fine; they're both 350 CID LT1 engines. I know there is a slightly different HP rating, but I doubt they'd make different clutch parts just for that small diff. There I go w/another assumption, though!

 

They are identical pressure plates: design, measurements, clamping force, everything. The clutch kits are identical except that the OE replacement disk for an F-body used a sprung hub whereas the OE replacement diskfor the Corvette used a solid hub because of the dual-mass flywheel. In fact, the hot ticket when converting to a solid flywheel has always been to just order the F-body clutch kit. So with that sameness comes the same problem for replacement parts: it's still the same piece of crap p/p and TOB sourced from China.

 

Huh. You'd think that w/the number of F-bod's there would be some decent options.

 

Spline count is different. I'd guess that the TOB ID is different too...

 

Here are some pics of my remachined PP and DM flywheel. I did a zf swap and needed some good clutch pieces. I spoke with both Jim and Bill at great lengths about this. They were both a little skeptical about this but after seeing the results, wanted some info on the process. The correct height for the standoff to friction surface is .190 to .195. One thing to consider is if you remove material from the standoffs, you have to put a spacer under the bolt heads to prevent them from bottoming out in the counterbores of the bolt holes in the flywheel.