I need clutch help

gadams · 09-09-2004, 10:11 AM

I need help, I just replace my clutch, pressure plate and T/O bearing and my clutch slips.

about a year ago I had my trans rebuild and replace the clutch and pressure plate while it was out. At first the clutch worked great then at about 100 miles it started slipping. I tried to adjust the linkage but no luck.

This week I went back in and replaced the clutch and pressure plate again thinking I had a bad pressure plate, put it back to gather and it still slips. I have adjusted the linkage in, out and per specifications.

The only thing I did not touch (either time) was the flywheel, I did inspect and it appeared to be in good shape no excessive hot spots.

I would like some opinions on what the possible cause might be before I go back in.

am I adjusting the linkage incorrectly?
is it the pressure plate?
bad clutch or pressure plate
other?
Give up at let someone else do your work?

greg

gadams · 09-09-2004, 02:42 PM

If it matters the car is a 77 930

greg

Superman · 09-09-2004, 03:06 PM

Of course, you would adjust the linkage to fix this problem. But if that does not work, then I'd ask whether your flywheel has ever been resurfaced. JW has warned us about resurfacing without using a special diamond grinding wheel. The grinding wheels that are not this special kind will not be sufficiently square on the edge. This causes the corner of the flywheel business surface where that surface ends at the ridge which is at the outer edge of the flywheel to be rounded unstead of square. So, when the pressure plate is bolted on, it does not settle all the way down to the flysheel's business surface. This leaves a too-great distance between the flywheel business surface and the pressure plate business surface. With this dimension, a thousanth or two is a lot. Just a guess.

gadams · 09-09-2004, 03:21 PM

The flywheel has not been resurface or ever removed for that matter.

I started with adjusting the linkage but no matter haw it was adjusted it slipped.

FWIW I went ahead and dropped the engine, I will pull the flywheel and have it resurface. I sure would like to find the source so I do not have to drop the engine again.

greg

john walker's workshop · 09-09-2004, 03:23 PM

having freeplay between the two clutch levers is necessary so you know that the t/o bearing is completely releasing the pressure plate. you do the freeplay first, about a mm, then adjust pedal engagement point with the nuts on the cable sleeve.

gadams · 09-09-2004, 03:34 PM

Thank you, your input is greatly appreciated

that is exactly how I adjusted it the first and last time. then I tried every combination then gave up.

does this mean you do not think the problem is the PP, flywheel or clutch any or all?

greg

Gunter · Gunter's Garage

When you assemble the new clutch, the pressure plate clamps in the disk as you tighten up the clutch bolts. When these bolts get snug, how much space is there between the flywheel surface and where the pressure plate mates? That amout of space determines the clamping force on the disk. Is it possible that the release bearing is already pre-loading the plate because of improper installation? I am looking at the clutch schematic in an SC repair manual and there are a number of thrust washers and shims for the T/O bearing.

gadams · 09-09-2004, 04:31 PM

I went ahead and dropped the engine and it appears that the clutch is not pre-loaded.

Once the pressure plate was on I could not move the clutch disk so there was no space to speak of between the disk and the flywheel or the disk and the PP.

The 930 t/o bearing is pretty straight forward no spacers just center it and go.

I am concerned that the disk is not thick enough which would be exactly what you are getting at?

It appears it is thick enough to keep me from free spinning it but may not be think enough for my car.

thanks

greg

Gunter · Gunter's Garage

That's exactly what I mean. When you mount the pressure plate to the Flywheel and you put in the clutch bolts snug by hand evenly all around, before you start tightening with a wrench or socket, there is a space between flywheel and mating surface of the pressure plate. As you tighten up evenly one bolt at a time, this space deminishes until the plate is completely torqued to the flywheel. If the disk lining is not thick enough, there is no clamping. There needs to be a noticable space between both before you tighten up. How much? Ask someone like JW, phone him or someone who knows the setup. Good luck.

gadams · 09-09-2004, 05:03 PM

I went ahead and dropped the engine and it appears that the clutch is not pre-loaded.

Once the pressure plate was on I could not move the clutch disk so there was no space to speak of between the disk and the flywheel or the disk and the PP.

The 930 t/o bearing is pretty straight forward no spacers just center it and go.

I am concerned that the disk is not thick enough which would be exactly what you are getting at?

It appears it is thick enough to keep me from free spinning it but may not be think enough for my car.

thanks

greg

john walker's workshop · 09-09-2004, 06:24 PM

big HP engine, stock clutch? maybe the cable or pedal bushings are binding, not allowing full release.