clutch disc thickness question

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hepcat
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clutch disc thickness question

Postby hepcat » Sun Aug 18, 2013 5:25 pm

Hello,
I have a Chevrolet Silverado with a New Venture Gear 3500 transmission. The truck has just over 100,000 miles on it. Recently, I have noticed that the clutch doesn't seem to be fully engaged until my foot is almost off the pedal. I'm thinking that means that clutch disc is close to being worn out. I have found that the transmission bell housing was made with holes in it through which you can see the disc and pressure plate. I'm wondering if there's a way to determine how much life is left without taking the entire transmission out. I haven't been able to find any specs on how thick it is new and how much is the minimum acceptable friction material.

Could anyone offer advice?

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theholycow
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Re: clutch disc thickness question

Postby theholycow » Sun Aug 18, 2013 7:16 pm

I think you have to get a look at the face of the clutch to tell.

They're surprisingly thin when brand new. Here's a picture of a brand new one right out of the box, next to a used one of unknown age. The used one is the smaller diameter one. I think it must have been pretty close to new, I measured it with a digital caliper and as I remember it was almost exactly the same thickness as the new one.
Image

Here they are at their face.
Image
Image

If you get a good look at the face in person you can look at the depth of the slots and rivet holes. I guess if you look through your inspection holes and your clutch is a fraction of the thicknesses shown here (keeping in mind that yours is compressed between the pressure plate and flywheel, so the spring between the layers is compressed; look at the two layers individually rather than together) then it's probably done. Also see if you can see the slots, assuming it had them.
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kamesama980
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Re: clutch disc thickness question

Postby kamesama980 » Wed Oct 30, 2013 1:06 pm

Short answer: not difinitively.

I know 2 ways:
1: old clutch vs new clutch thickness is less than that of a dime. Old clutch defined as the vehicle not being able to get over 60 mph due to clutch slippage. new one still has paint.

2: .020" step on the flywheel is the difference between my car not getting over 30 mph and my 115hp truck pulling 6klbs 300 miles, twice, and still running fine after 3 years. Same clutch disk and pplate, improperly resurfaced flywheel (no step) in the cressida, new flywheel with step in the truck.

High engagement point is generally a sign of a worn but not yet failed clutch. My trucks the same way. it's a beater so the clutch is staying in till either I turn it into a sleeper with a 2JZ or it fails completely.
-Russ
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InlinePaul
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Re: clutch disc thickness question

Postby InlinePaul » Wed Oct 30, 2013 7:54 pm

Here is mine, changed out at 82,000 miles because of a failed throwout bearing. Disc was working fine though but getting thinner and we didn't want to drop the tranny a year later to to the disc.
Image
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mtheis
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Re: clutch disc thickness question

Postby mtheis » Wed Oct 30, 2013 9:25 pm

Here's mine during my restomod. Not sure how many miles were on it to begin with, but it still has plenty to go.
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