Technical Grinding noise and no drive

[Richenrygarcia]

Hello all. While enjoying a leisurely drive yesterday a grinding noise
erupted from the Cinquecento, and the stopped moving. Drive to the
wheel(s) had been lost but the motor continued to run. I thought the car
had "popped" out of gear but this wasn't the case. I was able to coast the
car to a safe stop, out of the way.

The gear selector works just fine. I can shift thought all 4 gears and put
it in neutral. When I put it in gear, release the clutch and press the
accelerator pedal, the grinding noise starts again.

I'm hoping a drive shaft coupling joint has stripped its splines as this is
an easier fix that opening the gearbox. Can anyone tell me how to determine
if this is the problem before I remove the hubs? Also, how easy are the
drive shaft coupling joints to remove and replace? The Haynes manual is
vague about the process and describes a means to determine bearing pre-load which isn’t very clear either.

Please see the attachment. The part highlighted in yellow is where I hope t he problem lies and the circled part is where I think the part which may have failed. I’m only thinking this because I’ve heard these parts are prone to failure and, at this point, don’t want to think about a bigger problem with the transmission.

 

[the hobbler]

There is a more than evens chance that the problem is that the splines in the coupling that slides on the drive-shaft have sheared off. If this is the case, it is a very easy job to rectify. You can easily check it by starting the car, a colleague (girlfriend, good mate etc) puts it into gear and releases the clutch whilst you look under the car. MAKE SURE IT IS PUT INTO AN AHEAD GEAR! (which is why I didn't suggest the wife!).If it is the coupling, the drive shaft will turn, but the sliding-coupling won't.
The job is very easy; put the rear of the car up on stands (NEVER, NEVER work under a jack)--undo the 4 bolts that hold the sliding coupling onto the rubber/alloy coupling--slide the coupling back up the drive shaft---remove the 'C' clip at the end of the drive-shaft--remove the sliding coupling (it will be a bit of a wiggle, but I assure you it can be done). Check the splines on the drive-shaft. There is a very good chance that the drive-shaft splines (steel) will be OK. Lubricate both the splines in the new coupling and on the drive-shaft liberally with grease (NOT copper-slip)--fit new coupling--re-fit 'C' clip, refit/replace the small spring in the end of the shaft (make sure that you get all the bits of the old spring out--it might have broken as the stub-axle and the drive-shaft would have been turning at different speeds)--bolt up the sliding coupling to the rubber/alloy coupling--make sure that the drive-shaft is sliding in the coupling(only a small amount of movement).
If one side has broken,I would suggest that you replace the sliding coupling on the other side, as a precaution.
The reason I know what the fault could be?---it has just happened to me as I was about to pull away at a set of traffic lights--in rush hour!!

 

[Richenrygarcia]

Hobbler, as always you are quick with an informative reply! I think I understand all you said and I’ll give it a check in the next couple of days. I just need to understand which part you think may be defective. Is this the sliding coupling you think could be at fault?

Thank you!

 

[fiat500]

Might possibly be the rubber coupling itself. The rubber disintegrates but not always obvious.
In my experience, partner, girlfriend or wife perfectly competent at achieving the task of selecting a forward gear with minimum 80% certainty.

 

[the hobbler]

Yes, those are the parts that I am talking about---the drive shafts are steel, but the couplings would seem to be cast iron, which is the weak point.

 

[Vitesse]

Yes, those are the parts that I am talking about---the drive shafts are steel, but the couplings would seem to be cast iron, which is the weak point.

This is a very confusing post Tom? Are you referring to the cast iron flange that attaches to the aluminium coupling as the weak point? I can’t see that the flange is the weak point, as opposed to the rubber inserted coupling?

 

[the hobbler]

I do assure you, having heard the noise,waited for the AA man to take me home and replaced the SLIDING flange, the splines were totally stripped off the inside of the flange. I think Fiat did that deliberately--the sliding flange can be replaced with just a 13mm spanner in about 40 mins,the rubber/alloy coupling is a much longer job requiring some big spanners, and as for the drive shaft!!!

 

[Richenrygarcia]

In either case, I hope the culprit is the sliding flange! It sounds like the rubber coupling is a lot more work to fix. I have time tomorrow to (or maybe tonight, if I'm lucky) to troubleshoot further. I'll let you know what I discover.

Thank you everyone for the assistance.

 

[fiat500]

I remember experiencing both problems in the olden days. I wouldn't say that one component was engineered to deliberately create a weak point, rather that a lack of permanent lubrication and possibly more powerful engine output these days puts an unconventional design under stress.
I'm sure the driveshaft splines are from harder steel than the ones inside the sliding-sleeve, but ideally they should be replaced as a pair.

 

[Richenrygarcia]

I remember experiencing both problems in the olden days. I wouldn't say that one component was engineered to deliberately create a weak point, rather that a lack of permanent lubrication and possibly more powerful engine output these days puts an unconventional design under stress.
I'm sure the driveshaft splines are from harder steel than the ones inside the sliding-sleeve, but ideally they should be replaced as a pair.

I don’t understand why they wouldn’t make both parts out of steel with the same hardness. This seems to be a fairly common problem after hearing about your experiences.

 

[fiat500]

I don’t understand why they wouldn’t make both parts out of steel with the same hardness. This seems to be a fairly common problem after hearing about your experiences.

If Tom's right about the flanges being made from cast-iron then I would agree with him that there must be some difference in hardness Not that it matters as It seems that the hardness may be less imporant than the alignment of parts. More debate here:

https://www.fiatforum.com/500-classic/352807-drive-shaft-drive-shaft-joint-wear.html

 

[Vitesse]

I do assure you, having heard the noise,waited for the AA man to take me home and replaced the SLIDING flange, the splines were totally stripped off the inside of the flange. I think Fiat did that deliberately--the sliding flange can be replaced with just a 13mm spanner in about 40 mins,the rubber/alloy coupling is a much longer job requiring some big spanners, and as for the drive shaft!!!

Well I have never had to replace a driveshaft due to stripped splines in all my time owning my 500, about 30 years I think, but I have changed loads of rubber couplings.

Is it not more probable that because you are driving a tune car that you have effectively created a weak point that you wouldn’t have on a standard car?

 

[the hobbler]

I agree with you Peter--in a perfect world both the shaft and the sliding coupling should be changed together. However, before I fitted my new sliding couplings on to the car, I checked them on a brand new (still in its wrapper) drive-shaft and realised that there was a very small amount of 'play' between the splines on the coupling and the shaft, and it was just about the same amount as between the new sliding coupling and the 'old' drive-shafts. I therefore cleaned and then liberally lubricated the splines on both the coupling and the drive-shaft with a Lithium grease before fitting the new couplings. A bonus is that the very slight 'clonk' that I sometimes heard when taking up the drive has also disappeared.

 

[F123C]

If the car isn't moving at all when you select a forward gear and engage the clutch, there's no need to get someone to help - just chock the front wheels, apply the handbrake, start engine, engage 1st gear and release the clutch, go around to the rear of the car, lie down and take a look - if the shaft is turning, then as others have said, the most likely scenario is that the driveshaft flange splines have failed. DON'T be tempted to reach in and touch anything while the shaft is turning, just look....

I've never seen these drive flanges fail if they've been kept lubricated - used to be part of a full service in Fiat dealerships. Any such drive flanges I've had to replace were very rusty. The rubber boots that fit onto the lip of each drive flange are there for a good reason - to keep water and abrasive grit out, these boots often perish, leading to premature, unnecessary wear and ultimately failure.

Anyone worried about any lubrication applied to the splines adversely affecting the rubber in the couplings, could always 'paint' the exposed rubber with something like silicone type gasket sealant to keep the lube at bay.

If the problem does indeed turn out to be a failed drive flange, best to (as 'the hobbler' has said) replace both sides. Also if ordering parts, best also order 2 new rubber boots and 2 new springs that fit inside the end of the driveshafts, you'll likely need them.

Al.

 

[F123C]

I agree with you Peter--in a perfect world both the shaft and the sliding coupling should be changed together. However, before I fitted my new sliding couplings on to the car, I checked them on a brand new (still in its wrapper) drive-shaft and realised that there was a very small amount of 'play' between the splines on the coupling and the shaft, and it was just about the same amount as between the new sliding coupling and the 'old' drive-shafts. I therefore cleaned and then liberally lubricated the splines on both the coupling and the drive-shaft with a Lithium grease before fitting the new couplings. A bonus is that the very slight 'clonk' that I sometimes heard when taking up the drive has also disappeared.

That's a very good way of checking for driveshaft spline wear if you just happen to have a brand new driveshaft to hand.

By the time some of these driveshaft spline problem cars came to me, lack of lube hadn't just caused the drive flange splines to fail but had also caused wear on the driveshaft splines, and not along the full length of the splines either - this could result in the new drive flange being hindered in moving freely along the driveshaft as the suspension moved up and down, as it could 'catch' on the wear lip on the splines. In these cases, there was obviously wear on the driveshaft splines which would shorten the lifespan of the new drive flanges. I often found rusted/broken springs inside the driveshaft ends also. (lubrication might have helped...).

I wonder if there is room to drill, tap and fit a grease fitting in the drive flange for ease of future maintenance?

Where I worked, we always checked/lightly lubed these drive flanges during a service, plus when road-testing, we always went on and off the throttle a few times to double-check for clonks etc.

Most customers wouldn't pay for new driveshafts (plus fitting) until they had no other choice, so often we had to fit just new drive flanges and hope for the best. Strange that when these failed shortly afterwards , the customer often couldn't remember our previous recommendation and expected the work to be done 'properly this time' (i.e. new driveshafts and flanges) at our expense.... :bang:
Some garages, even fitted a secondhand gearbox if the driveshaft splines failed, rather than strip the g/box and fit new driveshafts.

Al.

 

[F123C]

I don’t understand why they wouldn’t make both parts out of steel with the same hardness. This seems to be a fairly common problem after hearing about your experiences.

There might be several reasons why Fiat chose to make the parts from different materials - e.g. cost, ease of production etc.

I don't think it's a good idea to have 2 parts of the same exact material (including hardness after heat treatment), rubbing against each other (as in sliding splines) or turning on each other - in engines, shafts turn on bearings or in bushes of a different material, valves and valve guides are of different materials, most gears in gearboxes turn on bearings or bushes. It might also have been as some have suggested, that the easier and cheaper part is 'sacrificial', either by design or by good fortune

It's a long time since I studied properties of metals/material science but I vaguely remember cast iron as having some useful properties including some self lubrication due to carbon inclusion and that the surface is slightly porous and so can hold a little lubrication. (might be one reason why most engine cylinders used to be made from cast iron?).

(I'll say nothing about chrome plated alloy or Nicasil etc. cylinders other than they're great...... until they go wrong :bang: ).

Of course, Fiat might have chosen cast iron? (or are they cast steel?)for these drive flanges simply because of cost....

Al.

 

[the hobbler]

Completely agree with your previous comments regarding customer's memories Al. Even in a Mercedes garage we ran into that problem or, "it was only with you a week ago". This got to the point that our boss insisted that even if a car was in for only a light bulb change, oil, water and screen-wash levels were checked and rectified, at no cost to the customer---it cut the number of return visits for "my screen washers have stopped working and the car was only with you last week" type scenarios dramatically. At the 'Classic Friendly' garage I now work at, I have convinced them to put all "warning" comments IN WRITING on the invoice---has saved them a lot of hassle and un-warranted costs due to customer's lack of memory (accidental OR deliberate)

 

[Richenrygarcia]

Apparently this is a well documented problem on the Italian Fiat 500 forum. There's lots of good information in this 8 page thread. Google translate is a big help as all the conversation is in Italian.

https://www.500forum.it/forum/viewtopic.php?f=20&t=16237&start=105

 

[Antgiu]

We had the couplings go on ours. Was fine until we changed the gearbox output seals!
Replaced the old gungy grease with nice clean new stuff and, half a mile down the road came to a noisy stop.
Can not believe the immense torque of my engine was being transmitted via the old sticky grease!
The very end of the coupling had retained its splines as the driveshaft has a changer. Putting it on the driveshaft the wrong way round showed that the driveshaft itself was fine, so we just replaced the couplings.

 

[Richenrygarcia]

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.