Technical Diff bearing

[YeYe]

Hi all, I have a leaking gearbox diff seal (left side) and movement in the shaft, so bearing is gone. Does anyone know if I have to get both sides replaced? TIA.

 

[John202020]

I'd say just the faulty side once it's confirmed as needing replacement

 

[YeYe]

I'd say just the faulty side once it's confirmed as needing replacement

Thanks John. I thought so myself, but given that brakes and shocks are usually both sides together I just wanted to be sure.

 

[John202020]

Thanks John. I thought so myself, but given that brakes and shocks are usually both sides together I just wanted to be sure.

If it ain't broke don't fix it ?

 

[jackwhoo]

The shafts are spline fitted into diff gears,
Some inner cv joint movement is completely normal and not related to bearings

 

[Ralf S.]

Hi all, I have a leaking gearbox diff seal (left side) and movement in the shaft, so bearing is gone. Does anyone know if I have to get both sides replaced? TIA.

The problem seems to be just a leaky driveshaft seal. They're fairly straightforward to replace.

A duff bearing wouldn't necessarily make the driveshaft seal leak (unless it exploded and the seal became collateral damage). There should be minimal movement of the cup in the diff, so make sure-sure that there really is movement between the cup and the diff casing. Some play is okay but there should be no slop.

On the other hand, you might have play between the cup and the driveshaft itself (hold the cup still and try to rotate the driveshaft). If so, then that's most likely to be inner CV (aka spider, aka tripoid) wear. There's three rings in there, mounted on needle bearings, which sit in the indents of the cup/housing. Over time the rings can fret and wear grooves in the inner cup wall, allowing movement. If the cup has too much wear the driveshaft will clunk.. but it's not fatal in itself.

If the ring bearings wear out and fall out, then the driveshaft will make a grinding sound (the needle bearings get ground into paste by the rings, which will make the rings and the cup most likely KIA... but on the other hand, I drove a Stilo (with the same arrangement) from UK to Italy and back with just this slight occasional graunching noise, so it's not necessarily a disaster either. Funnily enough the cup survived that orderal.

A whole new driveshaft is the easiest option (look for "J&R driveshaft Fiat 500" on ebay) but if the cup is fine and just the tripoid rings and/or bearings are FUBAR (as mine were) then you can buy just the spider complete with the little rings and new bearings for around 1/3 the price of a new drivershaft. If you need to replace the driveshaft seal anyway, *and the driveshaft/inner CV is knacked* I'd be inclined to fit a new driveshaft at the same time, but DIY and no cash, then just the spider can work, even if the cup has a little wear on it.


Ralf S.

 

[DaveMcT]

It’s near impossible to get a replacement inner CV joint. You almost always have to get used or remanufactured shafts.

 

[John202020]

I think, confirm what is actually failed then go from there it may simply be a drive shaft oil seal? Note different left and right

 

[YeYe]

Thanks for all the replies. My mechanic is going to replace the seal and see where it goes from there. Hopefully it's just a bad seal.