I wondered that as well. It's all gears inside. I even put the trans all back on the engine with it on the ground, stuck the driveshaft in and inserted a wrench into the U joint with a long piece of pipe on it to keep it from turning, put it in gear, put a socket/breaker bar on the front pulley bolt. I could turn the engine over (rotate the crank). Originally I could see some marks on the flywheel and pressure plate where the slipping occurs so I tried "roughing" both up with some 80 grit on a DA sander. I did the same experiment and it held!...until I put it all back in the car...
I have measured and adjusted the spacing multiple times. I also have removed the t/o completely to test the "holding pressure" theory and it still slipped. I have called (now Silver Sport) and talked to them. They confirmed my math and basically shrugged their shoulders.
Does the transmission marry to the bellhousing without needing force? I wouldn't bother putting the transmission back in anymore since you've narrowed it down to the flywheel/pressure plate/disc assembly. FWIW, the speedway discs can be lacking in quality. Make sure they have the wavy marcel spring between the two friction materials, otherwise it makes them more sensitive to chatter.
It sounds to me after reading this entire thread, that you have a clamping problem. Either the clutch disc is too thin, or the pressure plate is not adjusted from the factory correctly. You said it slips without the throwout bearing in the mix. So it has to be the clamping force is not enough, due to bad or wrong parts.
Everything makes it sound like that particular pressure plate is just flat not applying enough pressure to the disk. I've had that happen when gravel from a freshly chip sealed road got in the diaphragm because I didn't have a clutch cover on my 48 and I literally had to dig it out of the pressure plate on the side of the road with my wife holding the pedal down. Meaning some foreign material not letting the diaphragm work right. That would probably mean packing material in this case. One thing to check is if you have the original brand and part number of that pressure plate search it out and find out what it's original application was. Then search out the matching clutch disk and fly wheel as the flywheel it is supposed to work with may have a raised contact surface. I can't remember the setup or vehicle but I have seen at least one that way but can't remember what it was on. Ehen someone is doing mix and match out of a catalog they are looking for bolt pattern and surface area and may not know the full deal on the intended application.
It goes most of the way in until it hits the spring on the t/o bearing and I can't raise, wiggle, push and hold it and get a bolt in. The spring pushes it back a little. I'd say it goes in within 1/4 to 3/8". I can then get all the bolts run in by hand, then run them the rest of the way (back and forth) with a wrench. It's all back in right now, but yeah, I'm out of ideas aside from a new matched clutch set.
The hat and disc came from Speedway. They came in a plain box. No manufacturer names. Only their own part numbers, but it may coincide with a manufacturer's part number. Something to research.
Can I use a hydraulic throw out bearing with that? I've yet to get a definitive answer. The car is mosty finished. I don't want to have to redo the whole clutch pedal assy.
No idea.. I don't care for hyd clutch linkage personally. I think they are not nearly as reliable as mechanical....
You said that you observed clearance for the TO bearing at the clutch fingers. You also said you tried it without the TO bearing. Car still won't move. Ergo it's not the TO bearing or hydraulic system. Using logic if the engine is running and the TO bearing is removed the car should take off, just like starting in gear without stepping on the clutch. You removed the TO bearing and issue was not resolved. Leaving the clutch or the transmission as the culprit. Why is the flywheel turning but the clutch disc is not? Mechanical issue. Not backwards. You say you can see the fingers depress as the pressure plate is made flush with the flywheel. Think about why the assembly is spinning but the car is stationary. Seems unlikely that the clutch disc splined center has broken it's attachment to the facing. I assume the splines are in good shape. Put the transmission in gear while it's out and turn the input shaft and see if the output shaft moves. Are you sure the input shaft is not broken? Or output shaft? Keep the output shaft from turning and try to spin the input shaft. Good luck with this confounding issue and you will get it fixed. Like Sherlock Holmes said, if you check all the possibilities and it all leads to only one solution, that's it, you have found the answer.
Understanding that the hydraulic throwout bearing has a spring, you should be able to overcome that by hand when marrying the transmission. Having to pull the transmission in the last 1/4-3/8" with the bolts could be an indicator that something is pressing on the diaphragm fingers, and reducing the clamping force.
Its a wild shot but this is what happened on mine when gravel got in it. Foreign material between the diaphragm and the cover not letting the diaphragam go all the way back. It was pretty obvious on mine because several of the fingers on the diaphragm were not at the same height when I shined a light up in. I'm still more inlined to believe that there is something that just flat ass does not jive in that pressure plate. Possibly the wrong diaphragm inside it. Normally it is a case of Won't release like Billy had rather than won't hook up. there.
Have you bolted up the pressure plate without the disc and checked the distance to the flywheel. That might tell a story.
SO - your TO bearing assembly is disengaging the clutch by some distance (perhaps as much as) 1/4 to 3/8" before you even activate the TO / clutch pedal?
Have done all of that. Transmission is intact, (I described my method on another reply), center of disk intact, splines are all new, clean and never driven, rear diff intact, check, check and check. Thank you for the input.
If it didn't release, I think I could figure that out pretty easily. Never had a brand new one slip like this.
It slips even with out a TO bearing in it. Don't worry, I didn't start the engine to test this, just used the starter with the coil wire removed.
I have NOT done that. But just setting the disc on the pressure plate on the bench, there is about 3/16" or a little more of disc material above the p/p mounting tabs. But I will try that next just to see if something is fowling up in there when I tighten it down.
I can compress the spring with my hands but when I'm putting the transmission in I can't wiggle, lift and push all at the same time. And as I've said, it even slips without a T/O bearing in it. It's GOT to be something with the pressure plate/disc. I just haven't found the Ah HA! moment.
At this point after reading all the new input I think I'd make 1/4" spacers and install them between the Trans and Bellhousing and point the car towards the door. Put it in gear and start it with the clutch in. If it pulls release the pedal and see how it works out. Can you make it slip then? We used to have a rebuilder in Portland. They would build Comp clutches for us and we take the flywheel and disc to them and assemble it there. Then Walt would put it in his press with a gauge and tell us exactly how much disc pressure we had on the disc. Boy is that Old School talkin.
Not sure I follow you here. Space the trans back from the bellhousing? That will increase the space between the throw out and the pressure plate and cause it to not even touch. Seems the same as when I had the TO completely removed. Maybe I'm mis-reading you here.
Correct, I had forgot you did that. Can you leave the Trans mounted in the Chassis when you pull the motor? Set the park brake or have someone stand on the brakes and with it in gear use a lever of some kind and see if the input shaft might turn. That would indicate something in the gear box to look for but I have no idea what that could be in a TKO.
Everything you have done points directly at the pressure plate not clamping the clutch disc to the flywheel. It's either a bad pressure plate or the wrong combination of pressure plate and disc. Since you have had it running and it was slipping, have you taken a really close look at both the flywheel and the disc? Is this a flat flywheel with no steps machined in?
I have a couple times, with the engine/transmission on the floor, put the drive shaft in, stuck a wrench thru the U joint with a pipe on the end of the wrench, put the transmission in gear and turned the front pulley bolt. Twice I've not been able to turn it (without rolling the whole engine off the stands). I can see and feel the output shaft turn and force the pipe against the floor and stop. But when I put it all back in the car, it would try to move...then start slipping again.
My thought is that disc is not thick enough and man is there a PP that the flywheel isn't drilled for?
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