Experience with modern clutch disks versus old?

[Timothy B.]

I am going to have to pull my transmission out of my 67 small block yet again for chatter that I believe is caused by a problem with my pressure plate. I have purchased a new AC/Delco clutch set (p/n 381146), which by the way is a Sachs pressure plate and disk. The LUK set I installed last year has never worked right, so I am starting over. I suspect that the balance shop who opted to weld weight on the pressure plate might have warped it.....

Here is what I request input about: New sets come with clutch disks that are surfaced with a modern replacement for the old style asbestos type. When I installed the clutch last year I first installed the new clutch disk with the new material. I found that the clutch was hard to engage smoothly as it grabbed much more quickly that the old type disk. I could also audibly hear a friction sound during clutch engagement. I drove the car 2 months that way trying to get it to wear in - but it didn't get any better. So, I pulled the trans back out and put in the old type disk that was not worn out. Low and behold it engaged much more smoothly and quietly.

From this forum, I would like to know if it is common that the newer disk material does indeed feel different in the way I have described?? Is my experience typical or not? I have to decide when I pull the trans again whether to install the new disk (stamped Valeo on the friction material) or to install again my old asbestos disk? Does it just take a longer time for the newer material to wear in and smooth out than the older type?

Attached below is a photo of the two types of disks and also an old thread from last year on this topic. The one on the right is a LUK disk, but my new Delco/Sachs disk looks similar. I didn't get a clear feel from the responses last year whether or not others have also noticed a difference in engagement feel, and that is what I am after here.

https://www.ncrs.org/forum/archive25.cgi?review=222272

[John H.]

Re: Experience with modern clutch disks versus old

Tim -

I've used several LuK clutches over the last ten years in various cars, and have never had a problem; LuK is the world's largest clutch manufacturer (and OEM supplier), and Sachs is a LuK subsidiary. Asbestos was removed from clutch discs many years ago, and the modern friction materials have been in use for a long time. Did you have the flywheel surfaced when you installed it?

[Joe L.]

Re: Experience with modern clutch disks versus old

Tim-----

I wouldn't count on that old disc lasting too much longer. Of course, if the car is very limited use, it may last as long as you need it to.

I also agree with John---the new clutch material ought to work fine (even though I have not used it). I mean, this material has been used in PRODUCTION clutches for more than 10 years with no problems that I've ever heard of. Valeo (apparently, the manufacturer of the friction material) is another of the world's major clutch manufacturers and MAJOR supplier to the OEM market for clutches and many other components.

I doubt very much that the pressure plate cover was damaged by the welding-on of weights. This is a VERY common method used to attach weights to balance the pressure plate assembly.

[Stephen L.]

Re: Experience with modern clutch disks versus old

Spend the bucks to resurface the flywheel. Even if it looks good, it more than likely will give some chatter.....
If you had it resurfaced take it back and have them do a runout to insure its flat. Had a flywheel from the factory on a new car that chattered when it came off the truck.... after many "solutions by the dealer" found the plate had been ground at an angle at the factory.

Been there done that.

[Timothy B.]

Re: Experience with modern clutch disks versus old

Thanks for the responses to my question. I am now leaning on trying the new disk with the new material since folks seem to have good luck with them.

Regarding the other comments, yes I had resurfaced the flywheel. I had trouble initially getting it done correctly (as some of my posts from last year documented, including a 'lessons learned' posting I had created). In the end, I had the flywheel in good shape prior to the last time things went back together.

As far as the pressure plate goes, the balance shop seemed to have to do allot of welding to it, and he just welded beads of material to it to add weight, and I could see the heat affected zone clearly. I won't go back to that shop again as I didn't get a good impression from the guy as to his work. Also, the fingers that contact the throw-out bearing were not even apparently, resulting in a vibration feel when I start to engage the clutch. When I install the new parts this time, I am going to make sure the fingers are resting at the same height above the flywheel with everything bolted up before I put things back together.

[Joe L.]

Re: Experience with modern clutch disks versus old

Tim-----

I've never seen anyone use weld beads, alone, as a measure to add required weight. It could see it being done if very small amounts of weight were required, though. Usually, a washer of the approximate required weight is tack-welded to the cover.

[Joe L.]

Addendum

Tim-----

I forgot to add: it's important that the fingers of the clutch diaphragm spring be properly aligned. They should all be "deflected" to just about the same degree.