Technical Problem with transmition, please help

[gordinir8]

When i bought the car i noticed that the drive shafts had an end-play of about 2cm both ways from the differential to the flexible couplings. Looked strange but i said it is ok at the time.
Moving the drive shaft at both directions is very easy with no great force needed, kind of free play. Today as i was driving in a hill suddenly transmission lost its grip.
Stopped the car, put first gear and push the car with my hands. It just moved with no problem and i said that's it, Gearbox broke down. Then i noticed that while i was pushing the car fwd the L/H side drive shaft was turning in the opposite direction of the wheel (because of the differential).
Then idea came and i push the L/H drive shaft that was all the way in, into the diff, towards the Flexible coupling and it was reengaged again with the coupling. I drove my car back home with no problems.
According to Haynes manual exploded view of the rear hub parts, there must be a spring between the drive shaft and hub shaft probably preventing the shaft to move freely in and out of the diff or flex coupling. Do you think that my car is missing those two springs? What about yours? can you move the shafts in and out with almost no force?

 

[gordinir8]

And here is a link video about what i mean, Ofcourse now that i am thinking of it again, springs will make it even worse since they will push the shafts away of flex coupling.

 

[Toshi 975]

That amount of end float looks excessive to me. As for those springs they never seen to last very long and half the time they are broken when the driveshafts are removed. I think that the first thing to do would be to check the splines on the drive shaft ends and coupling. Also there should be circlips at the end of the drive shaft which would restrict the end float.

 

[fiat500]

There should be a big circlip set into a groove on the end on that shaft near to the spring. More likely that it hs fallen off or disintegrated.
Remove the 4 bolts holding the drive flange to the hub and I bet it will just pull off the splines....it shouldn't. There may be something wrong at the gearbox end but the shaft should be able to slide so it seems correct.
Once disgnosed you may be best to renew the seal inside that big rubber cover at the gearbox end as it may have been damaged.
Also replace the rubber at the driven end.
No worries, this is an easy fix.

 

[gordinir8]

"Also replace the rubber at the driven end"

Peter you mean the rubber close to the gearbox?

I might go down later for a quick ts

 

[fiat500]

You can probably re-use all the rubbers if you want to. But the at the end where the trouble is it usually needs replacing as it cracks and splits very easily.
There is a seal in the rubber boot on the gearbox side. It is carried inside a metal or plastic housing which is easy to remove. The seal is often worth replacing as you will have access to remove it. If the big rubber part is OK then I would not change that because modern replacements can be very poor.

https://www.fiatforum.com/500-classic/422377-seriously-no-gearbox-fluid-leaks-2.html

 

[gordinir8]

Previous owner had change those two big rubber boots but don't know about the seals inside, i will ask him. To be on the safe side i am planning an engine/gearbox overhaul otherwise i will have problems all the time, ''been there done that'' Besides this engine is leaking from every joint so overhauling is the only way.
Thank you all so far for your help, i am afraid that someone will shoot me in the end after all those questions.

 

[gordinir8]

Removed the 4 bolts from the coupling sleeve and it just came out of the splines ''as you said'' since there was not circlip nor a spring. If it was i wouldn't have that problem. Shaft spline is also worn and It seems to me like it is impossible to put the coupling sleeve into the spline, then a circlip and then screw back the 4 bolts in to the rubber coupling, looks like if it was secured with the circlip the coupling sleeve can't touch the rubber coupling by 1-2mm
if you understand what i am trying to say. of course all this with the car raised and drive shaft not parallel with the ground, i maybe gain that 1-2mm if i lower the car. Also not sure if i can secure a circlip since the groove is not 100% deep because of the damage. Coupling sleeve spline is acceptable to me.

 

[jjacob]

You need to buy an axle kit. It will come with new axles, cast iron driveshaft flanges, springs, clips, and all boots. You should also replace the flexible joints.
Axle kits run around 80-100 euros, and the flexible joints are around 30 for a set.
Transmission will have to be removed.
John

 

[gordinir8]

My shafts are 19mm and not 25. looks like 19mm are more expensive and i was wondering if i can upgrade to 25mm which are also cheaper.
I will first try and see if a circlip can save it.

Thomas

 

[fiat500]

No worries, this is an easy fix.

Not true now....although it is still an easy job, but inconvenient and will take a lot of time.
You said you will be making major changes to the engine and transmission, so maybe you could do a quick fix to keep you going for now?
Can you get hold of a replacement driven flange...maybe already used? It would be better than the current one which will have matching damage at the opposite end.
Fit that back on the shaft and if a circlip will not stay secured, just weld it in place or even weld in a big washer. It doesn't take much strain in normal use.
Use lots of grease on the splines and you should be OK for enough time to think about the longer term solution.
You won't be able to dive up Mount Olympus but OK around the city,

 

[gordinir8]

If i ever need to drive at mount Olympus i will certainly need the help of all 12 God's (we still have 12 god believers here!!)
Back to reality for what i saw, driven flanges (those with four bolts) does not have the same damage at their splines. If circlip can secure the shaft i will have no problem with this tremendous horsepower. spot welding might be a solution.
I have also a plan B but i will first try with the circlip. Gearbox o/h is not on my list know, i need to do first the engine. When i strip the gearbox and it is a mess everywhere i might go for a 126 type.

 

[F123C]

My shafts are 19mm and not 25. looks like 19mm are more expensive and i was wondering if i can upgrade to 25mm which are also cheaper.
I will first try and see if a circlip can save it.

Thomas

Worn splines on shafts can be either metal-sprayed or built-up with weld and recut. Usually only done when replacement parts are no longer available or extremely expensive.

Pricey to have this reclamation done but if you know someone in this line of work who owes you a favour.....

Just a thought :idea:

Al.

 

[F123C]

You all probably know this already but for guys new to the 500 etc :-

Iirc the 500 uses a cardan? joint at the inner end of each driveshaft where they attach to the gearbox(transmission) under the big rubber boots.

If you pull the driveshaft too far out of the differential the little drive blocks can fall off the driveshaft cross-pin inside the big rubber boot.. To re-attach them you'll have to unbolt the rubber boot. To check if they're still in place correctly try twisting the driveshaft back and forth, minimal movement means they in place ok.

Al.

 

[gordinir8]

If I understand well are you talking about part No.1 ?

 

[fiat500]

Don't worry Thomas and Al,part No.1 can't fall out unless something really disastrous had happened. That is the issue; to put in new driveshafts you need to remove and dismantle the differential.
By the way, you may know this by now, but the 19mm shafts can be directy replaced by 24/25mm ones both in the synchro and non-synchro box. Just make sure they are specified for the 500 box.

https://www.fiatforum.com/500-classic/445012-difference-126-v-500-25mm-driveshafts.html

 

[gordinir8]

I now that and I am planning to replace them with 24/25, besides they are cheaper also. I put a circlip on at the shaft but the coupling sleeve couldn't touch the rubber coupling so I put four spacers. Don't ask me what is going on it just look that the shaft is missing as I said in my previous post 2-3 mm. This is a temp solution until o/h.

 

[fiat500]

Maybe the rubber coupling is fitted the wrong way round...It looks new. Or some other reason makes the big axle nut too fat out? Either way, taking off the coupling might mess up the bearing pre-load...Assuming that is setup OK. Sounds like the previous owner wasn't a good mechanic like you Thomas.?

 

[gordinir8]

As I always say the best mechanic for my car is me, for your car is you and goes on.
As for the rubber coupling which are new I will see if it is possible to install either way out that might be the answer.

Thomas

 

[fiat500]

I think the inner splined part is slightly longer; at the side that faces the wheel I think. It must bear on the centre part of the inner wheel bearing I guess?