Technical 850 Coupe gearbox changed and clutch judder started

[vili76]

Hi! Had my Fiat 850 Coupe 1967 gearbox changed last summer to a refurbished one (I think it might be from an 850 sedan) and with taller gears, so gave up on the acceleration to get a less revving car I guess. Also changed the whole clutch assembly along with other parts involved like the small bronze bushing in the camshaft. So every related part, flywheel too, should be fine, new and in order. Also new tranny and motor mounts.

Still after the change the car developed a clutch judder when starting from first gear, especially when starting uphill and totally unbearable when starting uphill with more load like 2 people along in addition to the driver.

So all the parts are checked, clutch has been out a few times and no oil on the surfaces or such. Can this be related to the taller gearing? I have checked around and googled my a** off but nowhere it has been said that a certain 850 gear box is incompatible with the Coupe standard engine.

Some have suggested that there should be a "bend" in the clutch cable cover tube when installed and if this is not there it might cause this?

Please help if you have any ideas. We have run out of parts to replace and ideas to try.

 

[bugsymike]

Hi! Had my Fiat 850 Coupe 1967 gearbox changed last summer to a refurbished one (I think it might be from an 850 sedan) and with taller gears, so gave up on the acceleration to get a less revving car I guess. Also changed the whole clutch assembly along with other parts involved like the small bronze bushing in the camshaft. So every related part, flywheel too, should be fine, new and in order. Also new tranny and motor mounts.

Still after the change the car developed a clutch judder when starting from first gear, especially when starting uphill and totally unbearable when starting uphill with more load like 2 people along in addition to the driver.

So all the parts are checked, clutch has been out a few times and no oil on the surfaces or such. Can this be related to the taller gearing? I have checked around and googled my a** off but nowhere it has been said that a certain 850 gear box is incompatible with the Coupe standard engine.

Some have suggested that there should be a "bend" in the clutch cable cover tube when installed and if this is not there it might cause this?

Please help if you have any ideas. We have run out of parts to replace and ideas to try.

If you are happy there is no oil on the friction area to cause the judder, is there any distortion on the clutch plate etc. Not being rude but after 50 odd years in the motor trade I have seen some issues caused by fitters "hanging" the gearbox off the clutch whilst trying to align it causing damage.
I assume you meant the crankshaft centre bronze bushing in the centre of the flywheel that supports the first motion shaft of the gearbox, I usually put a little copper slip grease or similar on that bush and also would check it was a nice free fit on the gearbox before fitting in crank, though in fairness if that was at fault usually it would cause a noise when clutch disengaged and possible grating when engaging first gear as it would cause a drag.
Also when fitting the clutch check the centre plate slides easily on the gearbox splines and that the clutch release arm moves smoothly.
I don't know about a bend in clutch cable tube, but generally on cable clutches I would go for as gentle a curve as possible to prevent a jerky operation, so if it doesn't feel smooth and easy pressing the clutch pedal when stationary I would be suspicious of it.
If your clutch is the older design with six springs rather than modern diaphragm clutch, then from new they can be a little fierce until bedded it. Back in the 1970s we used to have bets on how many time the customer would stall pulling away on certain models of car after a new clutch was fitted.
If all else is correct as a last resort to aid bedding in , you could try a bit of slipping the clutch to take the edge off it, only a little though!
Finally if taller gearing on first gear with different gearbox this would exaggerate a problem but not be the cause.

 

[vili76]

If you are happy there is no oil on the friction area to cause the judder, is there any distortion on the clutch plate etc. Not being rude but after 50 odd years in the motor trade I have seen some issues caused by fitters "hanging" the gearbox off the clutch whilst trying to align it causing damage.
I assume you meant the crankshaft centre bronze bushing in the centre of the flywheel that supports the first motion shaft of the gearbox, I usually put a little copper slip grease or similar on that bush and also would check it was a nice free fit on the gearbox before fitting in crank, though in fairness if that was at fault usually it would cause a noise when clutch disengaged and possible grating when engaging first gear as it would cause a drag.
Also when fitting the clutch check the centre plate slides easily on the gearbox splines and that the clutch release arm moves smoothly.
I don't know about a bend in clutch cable tube, but generally on cable clutches I would go for as gentle a curve as possible to prevent a jerky operation, so if it doesn't feel smooth and easy pressing the clutch pedal when stationary I would be suspicious of it.
If your clutch is the older design with six springs rather than modern diaphragm clutch, then from new they can be a little fierce until bedded it. Back in the 1970s we used to have bets on how many time the customer would stall pulling away on certain models of car after a new clutch was fitted.
If all else is correct as a last resort to aid bedding in , you could try a bit of slipping the clutch to take the edge off it, only a little though!
Finally if taller gearing on first gear with different gearbox this would exaggerate a problem but not be the cause.

Problem solved! All it took after all was two washers on the clutch cable (where the clutch cable cover meets the bracket on the side of the gearbox. So the geometry was a bit off for one reason or another after changing to a new gearbox. But the problem did not go away with removing the whole package, dismantling and putting back together so it might be that the small bracket for the cable was slightly different angle from the old one or something similar. Anyway the car is running without judders now! The clutch is noticeably stiffer but I guess that's just for me and my left foot to learn to work with it.

 

[bugsymike]

Problem solved! All it took after all was two washers on the clutch cable (where the clutch cable cover meets the bracket on the side of the gearbox. So the geometry was a bit off for one reason or another after changing to a new gearbox. But the problem did not go away with removing the whole package, dismantling and putting back together so it might be that the small bracket for the cable was slightly different angle from the old one or something similar. Anyway the car is running without judders now! The clutch is noticeably stiffer but I guess that's just for me and my left foot to learn to work with it.

That's good and should get easier as the clutch wears in a bit.
The cable looks fairly old, so if a good quality new one was fitted it may get even smoother.
Maybe the new gearbox casting was designed slightly different altering the geometry, it doesn't take much to alter the cables alignment.