Technical clutch

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Technical clutch

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Apr 1, 2017
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Afternoon all....


My clutch has a very finite biting point about 2/3'rds up and is quite abrupt when setting off......


Before I start stripping things apart any pointers?


Thanks in advance.....


Rob
 
Have you checked that the clutch operating cable is correctly secured to the side of the gearbox? There is a curved lug at the clutch end of the cable's outer sheath--this locates into a matching groove cast into the side of the gearbox, just under the cable securing stud. Lack of correct location of the cable will result in clutch judder/fierce uptake.
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My clutch has been like that for the 20 years I've had the car, despite my paying attention to all the components involved. There might have been a subliminal improvement when I fitted a disc with a damper, but not a gamechanger. If there's a secret I'd like to know.
To my thinking, it's the combination of single-plate clutch, no shock absorber in the gearbox and very loose engine mounting that promote the rocking motion.
It certainly doesn't help if the cable is allowed to flail around, I agree.
It would be interesting to know how guys who coax a lot more power from the engine cope with the rocking couple, as there's only the rear mount and two flimsy rubber bushes to play with.
Or does anyone have details of how the Steyr-Pusch powerplant was mounted in the 500 ?
 
How low is your clutch pedal? As a rule of thumb I find that it needs to be about level with the brake pedal for correct operation.

Assuming the question is to me, the clutch pedal is about 1/2" higher than the brake, so plenty of travel. As I've said in another thread, I cope by letting the clutch engage and start moving the car off on idle, before giving it any gas. It works on the flat. Hill starts are never quite so smooth.
 
Assuming the question is to me, the clutch pedal is about 1/2" higher than the brake.

Yes Mr. Giardini, the question was for you and also the Whitakers and anyone else.....and so is this answer. :)
If the clutch pedal is so high then I suspect that you have no free-play before the pedal movement starts to disengage the clutch friction plate. I recommend that you check that at the clutch actuating lever and wind back the lock-nuts to introduce some. that will lower the pedal and the different angle might make clutch operation more controllable.
It sounds like you have replace all the mechanical items possible but whilst the Fiat 500 clutch is not the most sophisticated available, I don't think it should be as temperamental as you describe. It's possible that you have a worn guide or spigot bush in the flywheel. The end of the input shaft to the gearbox relies on this to keep it centralised. If worn, the friction-plate can spin off-centre which is one of several things that could cause your problem. Worn or soft engine/gearbox mountings will accentuate this but I think they would have to be very worn to actually cause it.
 
Mr. Giardini and Mr. Patinated sound like Reservoir Dogs characters ;)

Interesting point Peter, I've always set it up so that the clutch lever return spring returns the pedal to the stop with no slack in the cable. I will now try it your way and report any improvement.
Very good point also about the spigot bush in the crankshaft, I never thought of checking that, now on the list of next engine-off items of interest.
 
Mr. Giardini and Mr. Patinated sound like Reservoir Dogs characters ;)

?
It's not so much that there will be slack in the cable because the spring at the bell housing will pull the pedal to give tension.
Simply that there will be say 25mm of pedal movement before significant resistance is felt. Although this adjustment can be over a fairly wide range and still works, the Haynes manual does give a measurement which I can't remember. On my car I can now sense when it's time to adjust it because of subtle changes in the ease of changing gear.
 
To further help Rob the Whitakers endeavour, I've dug up a troubleshooting chart for clutch judder in a Fiat workshop manual: possible causes listed are
1) oil or grease on flywheel / disk / pressure plate
2) loose rivets anchoring ferodo to disk
3) disk center not sliding smoothly on shaft splines
4) damage to flywheel / pressure plate surfaces
5) alignment fault (that would be the spigot bush Peter mentioned)
6) faulty adjustment of the 3 lifting tabs (n/a if like me you have a diaphragm)
7) harshness in the pedal/cable operating mechanism
8) worn out ferodo (but they give no minimum thickness)

On 6-spring type clutch, spring free length should be 41.7 mm
Pedal free play 35 to 40 mm
Clutch disk maximum warping 0.15 to 0.30 mm

And one I don't quite understand: free play between shaft and disk splines,
lengthwise 0.05 to 0.10 mm, crosswise 0.15 to 0.30 mm.:confused:
 
there is an additional support / stabiliser available that is a steel cradle. It connects the gearbox to the chassis - used for tuned cars.
 
there is an additional support / stabiliser available

Could you post a link or picture of what this might look like ?
The only reference I found to a gearbox steady plate was on the Middle Barton site but no pic... Thanks.
 

That one links to the basic gearbox support which comes in two versions. The one for the 126/"R" is slightly different so that the following part can also be fitted:

https://webshop.fiat500126.com/tran.../others/cover-for-gearbox-bell-housing-bottom

the Fiat 500 cradle can easily be drilled out to make the stabiliser fit.

My experience is that when fitted to the car whilst retaining the original-type, aluminium engine-mounting, the stabiliser makes virtually no difference to wobble, clunking or shimmying of the gearbox/engine. My thoughts are that it is an item that is designed to accommodate shortcomings or particular characteristic of the later type of rear engine-mounting.

There is no natural tendency of the mountings Fiat 500 engine/gearbox combination to cause any "abruptness" of use of the clutch. It is possible for the rubber blocks that insulate the box from the cradle to become detached from their metal backings and for this not to be obvious when having a cursory examination of them; thiscan cause judder. Incidentally, I used to run a 126BIS....a poor and embarrassing relative of the Fiat 500. It has what appear to be a technical improvement on the 500 gearbox mountings. In practise I found them to be very soft and subject to regular failure.:bang:
 
Peter (in Nairn) has just beaten me to it---I was looking as he was typing! Axel Gerstl, part no:- 01145, in 'others' section of 'transmission. Sadly, it seems to be out of stock at the moment with them.
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I'm fitting an engine damper that connects the cylinder head to the bodywork via a damper to resist twisting of the engine as per race cars....should make for some interesting vibrations......
 
Not sure if you’ve cured this issue as yet...,
The clutch in my ‘F’ misbehaved with a uncomfortable shudder for several years...
the Hobblers advice (first reply) cured the issue instantly in my case, the outer cable needs to have a visable ‘arch’ between where the cable locates in the transmission tunnel & the clutch fork, securing it to the gearbox correctly achieves this....best of luck Dave
 
Ok guys finally got round to looking at this at the weekend....


The cable conduit that goes from the body and bolts onto gearbox wasn't on the best of health and didn't have a nice upward curve......


Full new clutch cable and the car is top dollar and great to drive now..


Thanks for the help and advice......


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