Clutch Judder

PostPost by: triumphelan » Sat Jan 13, 2007 10:09 am

Re my previous posts on my judder
I had replaced the engine mounts ,had the propshaft overhauled ,new gear box mount,checked /replaced suspension bushes , fitted TT drive shafts & checked clutch for oil contamination

I have just changed the clutch all 3 components and had the flywheel skimmed .The clutch was changed about 2years ago,6K miles for the same reason which it did not cure.
At that time I did not have the flywheel skimmed as it looked ok with a straightedge across it ,I could not get a 0.002 " feeler gauge between flywheel & straightedge.
The clutch is now very smooth ,I cannot say exactly what was the cure ,Different clutch or skimming the flywheel
The story of the clutch change .
Using a friends garage with a car hoist the engine came out easily ,new clutch fitted and engine back in ,in the same day .
Drove car off hoist ,it was slipping a bit as far as garage door ,about 30feet,then had no drive the clutch was slipping .Pushed back onto hoist checked release bearing setting and bleed the clutch ,Still slipping clutch.
Spent 2nd day scratching our head trying to avoid the the inevitable
3rd day engine out .Checked the all components were fitted correctly and not damaged ,they were all ok .Engine back in ,with the engine connected to the gearbox tested we had drive thro` clutch ,with 1st gear selected there was no drive thro` clutch ,we even tried turning the engine thro` the back wheels nothing .Engine out again [thank god for the hoist ]
Removed clutch from the engine and retrieve old clutch from bin, when looking at the driven plate the spline's in the center were a larger diameter UREKA .So with the driven plate pressed onto flywheel by the diaphragm thee was sufficient friction ,until it "shinned" up move the car 30feet
Phoned my supplier who said "not again " and checked their batch and found they were all of the larger spline dia.Another plate was posted off fitted and a happy ending was had by all
A good tip if you want to "tighten " up you gear linkage fit a new gaiter to your gear leaver
Regards John 1969S4DHC
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PostPost by: john.p.clegg » Sat Jan 13, 2007 3:12 pm

John

Just out of curiosity (sp) what size plate was the duff one ( 7 1/2,8,8 1/2) and what diameter and number of splines???

Thanks.
John :wink:
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PostPost by: triumphelan » Sat Jan 13, 2007 4:17 pm

John ,
I will take some measurements and get back to you soon .
Traffic is now a pleasure to drive in .
Regards John 1969S4DHC
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PostPost by: triumphelan » Sun Jan 14, 2007 12:51 pm

Both plates were 8" dia,had the same number of springs ,the boss that held the springs was 4.750" did and the both had the same number stammped onto them 53131
The incorrect one had 23 splines,the od of the splined shaft it was intended to fit was 1.030" dia. and the dia of the root of the splines was 0.920"
The correct one had 20 splines od of gear box intake shft 0.900" dia and the root dia of splines 0.800" dia
As you can see from dimensions the incorrect plate was free the rotate on the gear box intake shaft
I will try and send some photo`s
Regards John 1969S4DHC
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PostPost by: rgh0 » Tue Jan 16, 2007 8:58 am

John

I am willing to bet that what fixed your problem was machining the flywheel. Bedding in a new clutch is like bedding in piston rings in an new engine. Just as you need the right cross hatch pattern in the engine bores you need the right finish on the flywheel. If you dont have the right surface finish on the flywheel it may not bed in and you get the stick / slip judder on engagement.

cheers
Rohan
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PostPost by: triumphelan » Tue Jan 16, 2007 2:18 pm

You could well be right .But how many modern cars when having their clutch replaced have the flywheel skimmed??
Regards John 1969S4DHC
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PostPost by: type36lotus » Tue Jan 16, 2007 11:53 pm

I always do! :D
Mike Geiger
66 S3 Coupe', no more :-(
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PostPost by: rgh0 » Wed Jan 17, 2007 2:44 am

John

My local brake and clutch specialist which is a small but very well recommended operation in Melbourne with a couple of outlets run by a guy with 30 plus years experience in the trade always recommends to the owner that they reface the flywheel and pressure plate for any clutch driven plate replacement job for all cars new or old.

If you dont he will not warrantee that the new clutch will not judder. I dont know how many other clutch places make similar recommendations on their replacement work but I also dont know how many will give you a warrantee aginast clutch judder either.

cheers
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PostPost by: triumphelan » Wed Jan 17, 2007 7:47 am

Having never had a clutch replaced in any other car other than the S4 ,I am as usual talking cr@p
But I will, if I ever need a clutch replacing in the future have the flywheel skimmed just in case
Regards John 1969S4DHC
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