Richenrygarcia said:

I did some troubleshooting last night. I had the wife start the car, put it in gear and release the clutch, while I looked underneath at the axle shafts.

With the clutch released the right shaft does not spin. The left side shaft spins as does the coupling. This leads me to believe the left side is to blame.

Dumb questions:

1) With the motor off and the car in gear, I'm able to push the car with little to no resistance. It feels like it in neutral. Do you think this a symptom of the differential "disengaging" one wheel while the other side coupling has failed?

2) Even if the coupling on one side has failed, shouldn't there be enough torque to spin the other wheel and move the car via the transmission/differential? Or is this normal operation for the Cinquecento differential?

Again, grazie mille for all the assistance.

Click to expand...

If the coupling spins and as would the outer part of the damper coupling then that would tell me it's the rubber coupling that's gone, still not a major job but more complex than the slide coupling....


don't worry about been able to push the car whilst in gear, the way differentials work because there is loss of drive to one wheel it will seem like it is in neutral as that one drive shaft will spin rather than turning the gearbox etc....

Richenrygarcia said:

I did some troubleshooting last night. I had the wife start the car, put it in gear and release the clutch, while I looked underneath at the axle shafts.

With the clutch released the right shaft does not spin. The left side shaft spins as does the coupling. This leads me to believe the left side is to blame.

Dumb questions:

1) With the motor off and the car in gear, I'm able to push the car with little to no resistance. It feels like it in neutral. Do you think this a symptom of the differential "disengaging" one wheel while the other side coupling has failed?

2) Even if the coupling on one side has failed, shouldn't there be enough torque to spin the other wheel and move the car via the transmission/differential? Or is this normal operation for the Cinquecento differential?

Again, grazie mille for all the assistance.

Click to expand...

Edit...as said above )

The reason that the right side doesn't turn when the left side spins uselessly is because of the way the differential works. So all the symptoms are normal if something is adrift with the L/H driveshaft. From what you describe it seems the splines are not necessarily the main culprit , although they may be worn in any case. If the coupling spins in sync with the shaft but the wheel doesn't turn, the next most likely fail point is the deterioration of the rubber in the coupling previously highlighted by Tony Vitesse.

Obviously, if all four of the bolts which secure the cast flange to the coupling were missing or broken you would get the same symptoms, but this seems highly unlikely. There are other, deeper and even less likely reasons why the wheel isn't turning which would confuse the issue just now.

I would raise the left rear wheel from the ground and turn the wheel by hand so you can verify this. You may have to grip the driveshaft to keep it stationary as you do this.

Oops, I misspoke earlier then I said the coupling spins. Thinking back, the coupling does not spin, only the shaft.

Sorry for the confusion.

richenrygarcia said:

oops, i misspoke earlier then i said the coupling spins. Thinking back, the coupling does not spin, only the shaft.

Sorry for the confusion.

Click to expand...

:d:d:d

Richenrygarcia said:

Oops, I misspoke earlier then I said the coupling spins. Thinking back, the coupling does not spin, only the shaft.

Sorry for the confusion.

Click to expand...

Back to the easy repair then

I pulled the left coupling with minimal issues. The splines are almost worn flat. See the pics. It makes me wonder how long I’ve been driving with this condition, ready to break at the most inopportune time. At least this time it happened one mile from my house - thankfully.

I’m off to the autoricambi for a replacement tomorrow or Saturday morning. I'll let everyone know know it turns out.

Thanks to everyone who has posted, helping me with this issue. You’ve all been a huge help.

That is exactly how mine was, almost no splines left in the coupling. I would suggest that, for what they cost, you replace them both. If the 'good' one looks OK, keep it and you will have it available for an emergency. I would also recommend that you replace the little rubber boots, the end-of-shaft springs and the 'C' clips. Carefully clean the splines on both shafts, and then liberally lubricate both the shaft splines and the coupling splines with a good quality Lithium grease (the sort of grease that you would use in C/V couplings)--NOT 'copper-slip'.

Are there any tricks to replacing the rubber couplings? Looking at the diagram it appears to be only a castellated nut and cotter pin. Pretty straightforward, I hope.

If the rubber/alloy couplings look OK, leave them! It is NOT a 5 minute job--not just a case of doing up the nut and replacing the split-pin.

Got it! I won't touch the rubber bushing unless I have to.

Replaced the broken flange yesterday without too much effort. The new piece was a bit of a tight fit but it all went together without too many four letter words.

A test drive proved problem was fixed!!!


Thanks again for all the help troubleshooting this problem.

Richenrygarcia, did you replace just the damaged drive-flange or, as I suggested, both of them? The fact that it was "a bit if a tight fit" I wouldn't worry about, shows that there is not much play between the splines on the coupling and those on the drive-shaft. Did you remember to liberally lubricate the splines with Lithium grease?. If you haven't replaced the 'good' coupling, it might be wise do it in a quiet moment, then you know that they are both OK. Well done for sorting it all out.

the hobbler said:

Richenrygarcia, did you replace just the damaged drive-flange or, as I suggested, both of them? The fact that it was "a bit if a tight fit" I wouldn't worry about, shows that there is not much play between the splines on the coupling and those on the drive-shaft. Did you remember to liberally lubricate the splines with Lithium grease?. If you haven't replaced the 'good' coupling, it might be wise do it in a quiet moment, then you know that they are both OK. Well done for sorting it all out.

Click to expand...

Hobbler, I only replaced the broken coupling due to time. I will replace the opposite side when time permits.

At this point, after reading multiple stories on the Italian Fiat 500 forums about failed splines leaving drivers stranded, I'd consider it preventative maintenance to check (or replace) them periodically. I'll also add a pair of these flanges to my parts box when I move back to the US.