Hi All,
does anyone know whether the drive shaft splines wear at approximately the same rate as the splines in the cast joiner? ie. is the joiner 'thingee' a somewhat sacrificial part compared to the drive shaft?
My 500 has noticeable clonky drive take-up which is also evident when you rotate the shaft relative to the joint. I have a new set of joiners which I decided to fit, hoping that might de-clonk it. To cut a long story short, jacked the car up, dismantled the wheel ends of the drive shafts, greased the new joints and discovered they were the skinny shaft ones. @*#+!@#*!!!! As they say, reassembly is reversal of the dismantling.
So back to the original enquiry. If it's clonking does it mean shafts and joints?
Regards
Viv

Hi Viv,

The coupling, flange and axle all can wear and not necessarily at the same rate. Generally the thinner the axle the quicker they wear- there are 500N, 500D, 500F and 500R versions- the 500R are most durable and last very well if properly lubricated.
Generally if the coupling wears and is not replaced it will cause more load on the flange which in turn can wear the axle which will eventually strip the splines.
Check for movement between the flange and axle- if there is significant movement look at the axle spline- if there is no visible wear try replacing the flange and lubricate the splines with white grease regularly- I suggest every 5000km/3000mls.
The Couplings vary immensely in quality- original Fiat ones could last 20yrs+ but I have had reproduction ones fail in less than 6 months. If you can find NOS fiat ones that is the best option.
Hope this helps!

Hi Damon500,
food for though there. I will probably do the whole lot (shafts & couplings) because I believe I could see wear on the shaft splines. (Or was it the bright bearing area that the shaft and coupling would make?) I must confess I didn't look too closely, lying under the car spitting chips kinda discouraged me from a sensible inspection.
Regards
Viv

My memories of problems with those rubber couplings mainly centre on the rubber itself breaking up. This used to reveal itself as I tried to get up a steep hill. As said previously, you should keep the splines well lubricated but watch that surplus doesn't damage the rubber. I would have thought that the driven spline would be made of softer steel and that the shaft splines would be very hard. It should be easy to ascertain if the latter are really worn.

Yep, familiar with the rubber coupling packing up. I'll have a close look when I do the cast couplings.
That was my thoughts about relative hardness of the shaft vs coupling, hence my comment about the coupling maybe being a sacrificial component.
Regards
Viv

That wear pattern is the way it is supposed to work but if you get any ingress of grit or hard particles in there they will seat into the softer material and give you the opposite effect.

Hi Viv,
The longevity of the axles/flanges is largely down to the level of maintenance and greasing of the joint- when I worked on 500/126 models as an apprentice Fiat mechanic we were trained to squirt the grease gun into the outer axle boots when lubricating the kingpins as part of a service. It is still better to remove the bolts and lubricate the splines periodically, on my daily driver 500 I find that after about 18 months-2 years they are usually dry and require regreasing.

A new coupling will often prolong the life of a moderately worn axle- as a rule of thumb if you can feel sharp edges on the axle splines rather than a flat at the top of each spline the axles are due for replacement.

The outer couplings will often outlast the axles and flanges if not lubricated- having said that many of the reproduction couplings available are poorly made and fail rapidly- (I replaced the moderately worn 20+ year old Fiat ones in my 500F and one of the new reproduction ones shattered and lost drive within less than 6 months)

Don't be tempted by cheap couplings- some are so poorly aligned that they can actually cause the flange/spline to wear due to runout on the mounting face. If here is no evidence of wear in the rubber or excess movement don't replace them- it can do more harm than good!

Thanks Guys,
I'll start with new couplings and while doing it have a close inspection of the drive splines then decide whether they've got to change too.
Regards
Viv

Viv,

Have you replaced these parts yet? Did you decide to replace the flanges/shafts also?

The reason I ask is that my new shafts and flanges came in yesterday and I'm curious if you have the same situation as me: The only way the new flanges are going to go on the shafts is with a hammer! The fit between the shaft and the flange is really tight. The shafts won't slide into the old flanges either.

From what Damon has mentioned (and from my old shafts and flanges), the flanges should slide back and forth on the splines of the shafts fairly easily (and be greased). I've got to give some thought as to how to make this happen.

-bob

Hi Bob,
I haven't done anything yet, just taking it easy and restricting burnouts to the minimum.
But you're right, the couplings should slide easily on the splines, they'll be doing that constantly as the car goes over bumps and the wheels go up and down. Can you see whether the coupling and shaft have the same number of splines? Is it possible there is a Fiat (600?) with a similar looking coupling but different number of splines? Is there a build up of 'mill scale' or similar crud on one or both? They have potentially been lying around for 30 - 40 years and may be way less than 'new' old stock. Let us know what you find.
Regards
Viv

Hi Bob,
The tight flanges are not uncommon when new- some of the repro parts are not particularly accurate in tolerance.
Try swapping the flanges side to side and turning them to different positions to find a spot that is best.
You can try to tap the flange up and down the shaft a few times to see if it takes the high spots off.
If all else fails you could try to replace the flanges and see if you gain some more clearance or simply return to the supplier and ask for a refund/replacement.
Regards, Damon

Thanks guys,

The issue was with newly purchased 25mm shafts and hardened flanges.


There was a substantial mis-match between the shafts and the flanges such that I could only get the flanges on about ⅛ of the way...

I touched base with a machinist who concurred that the flanges were nicely made but the splines on the shafts were not well cut.

On mine, the spline grooves were too rough. In some instances, the grooves weren't deep enough but mostly, the splines were too fat. So, I followed his advice and using a largish three-square file, smoothed out the grooves and took out material where there was too much.

In case anyone else has this issue, what I did was paint the shaft splines with a felt-tipped marker. I then popped on the flange and smacked it down. Where they jammed, the ink from the marker would be scuffed off and I could see what had to be filed off. By doing this a couple of times, I was able to focus on only removing the material that was problematic and in short order, the flanges slid nicely onto the shafts...

FWIW, the shafts are made of a soft metal that filed off easily.

Cheers,