Lancia Motor Club

Model Technical and Interest => Aurelia => Topic started by: Zetaman on 08 April, 2013, 04:48:59 PM

Title: Aurelia Clutch Judder
Post by: Zetaman on 08 April, 2013, 04:48:59 PM
I am trying to help someone with a B24 Spyder who has a bad clutch judder problem.  It has the Lancia clutch with the aluminium cover holding the springs as fitted up to the end of the 4th Series B20.

The judder is only on take-up from rest, but otherwise everything is fine.

Drive train is in balance; centre propshaft bearing correct, new spiders, clutch release bearing & fork motion is good, new clutch springs etc.
Changing gear on the move is fine.  No vibration in motion.

He is ordering a new driven plate to see if it is this item.

Any ideas very welcome.

Thanks from Paul Mayo

Title: Re: Aurelia Clutch Judder
Post by: Parisien on 08 April, 2013, 04:52:52 PM
Linings haven't been contaminated? Correct distances between surfaces plus surfaces as they should be?


Title: Re: Aurelia Clutch Judder
Post by: Zetaman on 08 April, 2013, 05:55:01 PM
Thanks Parisien,  I think these issues are under control.

Title: Re: Aurelia Clutch Judder
Post by: Zetaman on 15 April, 2013, 08:27:12 PM
The following has been contributed by a friend, which I think may be of help to others.

I had to do quite a lot to my clutch before I was happy with it. The first thing to realise is that it is very marginal for the 2 1/2 litre engine. Clutch torque capacity is proportional to diameter and spring load. The diameter was chosen for the original B10 so to cope with the B20 with over twice the torque they had to pack it with a lot of spring load. In consequence the internal loads are very high. The release load is more than 1/2 ton so to maintain a reasonable pedal pressure and travel the travel of the pressure plate is only about a couple of mm. so every thing has to be in good order and with no slop between pedal and clutch . They knew it was marginal so put a bigger one on Series 5.

These are the things I had to do to mine.
1. Lightly skim the pressure faces of the housing and the cast iron pressure plate. This means a loss of spring pressure but if the springs are shimmed with "pennies" this must be done with care. Too much and the springs will chock and something will have too give!

2. Inspect the spring holes in the aluminium spring housing for grooves. The original B10 design had short splines on it's outer dia. to transfer torque to the body. I guess these bound because they machined them off and allowed half the torque to be transmitted through the springs in shear which is novel! This , plus centrifugal force on the spring causes the grooves. This probably does not matter but depends how bad they look. There is not much aluminium to spare.

3. The release fork is badly designed. The female spline is not full length so the bottom fork is much stiffer than the top and does all the work. you will probably find that the bearing carrier face on which it presses is much more worn at the bottom than at the top. The asymmetric load causes the pressure plate to cock and wears the aluminium housing, particularly at the front. Mine was only slightly worn at the rear but the front was over 10 thou oversize so had to be bored and sleeved. Arguably the wear on the forks can be left but this depends on how bad it is and whether the operating shaft and it's bushes are sloppy. To restore these means ,I think , dropping the transaxle.  I ground the indentations out and dressed the fork ends so they they took up pressure simultaneously on the centre line. To stop rattle I put a blob of MIG on the back side of the fork ends and filed to a nice fit. Most of the problem seemed to be due to the fork cocking on the shaft splines so I also put a bush in the unsplined hole at the top of the fork. The unsplined hole is not concentric so it needs a bush with an undersize i.d. which is then bored to be concentric with the splines and a size fit on the spline o.d. The operating shaft is not lubricated and is probably worn which will also lead to cocking. This may requires new bushes and the shaft built up and ground. I fitted grease nipples at top and bottom. The bottom bush is very heavily loaded and oilite bushes may not be up to the job.

4. The clutch plate needs looking at. If in doubt get it relined. The standard lining with the right o.d. has a larger i.d. The right size is available, but perhaps not off the shelf.

5. If the clutch is oily the seal that runs on the tube on the gearbox input shaft needs sorting, but oil can also leak between the shaft and the tube so this needs sealing on assembly.

Title: Re: Aurelia Clutch Judder
Post by: Brian Long on 18 April, 2013, 11:45:57 AM
My favourite topic!
My B12 had bad clutch judder and it was finally cured by fitting a fine 'O' ring inside the spool (TAV 32 item 18).
Originally, the gearbox end of this spool had a fibre washer, or similar, on it which sat against (TAV 32 Item 8). I think it is item 24. This seal is omitted or disintegrates allowing oil to pass between item 18 and the shaft it sits on (Item 37). Make sur ethat the castellated nut item 40 is done up tightly. If it is loose on disassembly it will have released the pressure on this sealing surface or it indicates that the fibre seal has disintegrated. Only a small amount of oil makes its way along here but it deposits itself on the inner face of the clutch lining waiting to be distributed by centrifugal force across the lining whenever the clutch is operated.
If you decide to put an 'O' ring inside the spool, check that it is on the clutch side of the last of the oil distribution holes in item 37.
My clutch has been shudder free for thousands of miles since this modification.
Another source of oil contamination is if the felt plug at the end of the input shaft (Item 37) is removed/disturbed. Oil is pumped up along this shaft from the oil pump at he other end of it and was meant to lubricate the bearing oin the flywheel.(TAV 27, Item 13). With the availability of sealed bearings, this is not necessary. I machined an aluminium plug and fitted it into the end of the shaft.
Good luck

Brian Long.

Title: Re: Aurelia Clutch Judder
Post by: Zetaman on 18 April, 2013, 05:14:28 PM
Dear Brian,
Thank you.  Your mods are similar to those done on a friend's B20 3rd Series, restored recently. 
PS Do you still want photos of B12s?  You asked ages ago.

Title: Re: Aurelia Clutch Judder
Post by: DavidLaver on 18 April, 2013, 10:03:22 PM

Mine ended up with a sealed bearing and a bung also.  It also had ridges to catch the springs.  It took several in-and-outs to get it right, but not an unpleasant task.  I love the HUGE retaining clip.


Title: Re: Aurelia Clutch Judder
Post by: Niels Jonassen on 19 April, 2013, 04:21:10 PM
Another possible cause of judder may be too soft mounting rubbers for the gearbox cum differential.

Title: Re: Aurelia Clutch Judder
Post by: Brian Long on 20 April, 2013, 12:28:31 AM
Dear Brian,
Thank you.  Your mods are similar to those done on a friend's B20 3rd Series, restored recently. 
PS Do you still want photos of B12s?  You asked ages ago.

Yes please, particularly interior and engine bay pics.