I have a 2011 Skoda Fabia 1.6l TDI Diesel with a 5 speed manual box that has just cracked open the differential casing.Occurred entering onto a main freway under acceleration. Loud thud, puff of smoke , thought I had ran over something.Pulled over and inspected the vehicle, saw oil spray in the engine bay. Strong smell of gear oil. Assumed it was possibly a drive shaft seal.

Vehicle still drives, no whine or noise, slight clutch shudder from 1^st gear possibly due to oil on the surface of the clutch.

Carefully and slowly got the vehicle back home, and removed the underbody tray to find the issue attached in the photos.

What do you think may have caused this, or is this something common with KFK version gearboxes?

46 minutes ago, TLee said:

What do you think may have caused this

Probably a bad casting (manufacturing issue) or impact damage. Look for any signs of corrosion on the broken surfaces.

I would say that the damage was caused by an internal component coming adrift and falling into the spinning differential.

I have seen this type of damage once before and it was caused by a internal bearing failure and causing excessive end float in the carrier allowing the final drive gear to smash against the housing, but truly the only real way to find the issue is to strip it down and check it out, could possibly be a broken end on the drive shaft or a clip that's come off

Earlier VAG gearboxes had the crown wheel rivetted onto the pinion and the rivets failed leading to this sort of damage but they switched to bolted crown wheels to avoid this however on my old Polo I had a bolt break loose and punched it's way out of the casing 

Thanks all for your replies.

(nige8021 and Murdockman,  I am expecting it to be something like what you have stated.)

Will be getting it out hopefully this week and will post the outcome here

I agree, spalling on the 1st picture does suggest something internal letting go.

Hi All,

Have the box out and have found the cause. Locking pin (18) in the parts image attached had given way, causing the short shaft (9) to slide through the spider gears (10) and that shaft then makes contact with the inside casing.

As soon as it starts removing case material and structural ribs from the inside of the diff housing (24), that material builds up, jamming between the case and the end of the shaft, causing more damage, until the case cracks open. The shaft (9) eventually fails, cracks and becomes even looser to the point if the vehicle keeps driving it can lock up. Somewhat of a safety hazard.

It also caused case damage in the clutch bell housing casing , (see image) allowing oil to get on the clutch face and wreck that too.

So new refurbished complete gearbox and clutch for around €1350.

Apparently the figure is around 3% with the KFK boxes in Volkswagen Auto Group VAG vehicles over 7 years old, and is a design flaw on the part of VAG that is not of great concern due to the vehicles being out of warranty.

Its common, but low in numbers in reality compared the number of vehicles using this box on the road.

Glad to see you solved the mystery ( all be it a costly one  ) 

very surprised to see this to be honest.

 

One thing you do expect is a manual box to last the life of a car, especially a premium brand.

On 03/05/2022 at 00:15, KenONeill said:

Probably a bad casting (manufacturing issue) or impact damage. Look for any signs of corrosion on the broken surfaces.

No way, that damage was something internal making a (successfull) bid for freedom.

58 minutes ago, J.R. said:

No way, that damage was something internal making a (successfull) bid for freedom.

Exactly the same damage I had on my Polo gearbox when the rivet's failed on the crownwheel