Input shaft

[David Pattison]

I have a 81 S3 on removing gearbox the input shaft came out easily, presume missing circlip, previous owner was driving the car with no clutch / gearbox issues. Is the circlip required? Can it be fitted without a box stripdown ?

[Sparky]

Hi!  The circlip is non-critical, so no strip really necessary.  Make absolutely certain you have a nylatron washer on the shaft though.

However, I do expect some to disagree with me...

[910Esprit]

I agree...   I think the snap ring is simply to retain the input shaft.  On assembly it is effectively redundant once the spring loaded input shaft is loaded against its thrust bearing (the Nylatron washer) .   If you do refit the snap ring, you need to remove the bellhousing, which also involves removing the 2 driveshaft housings.   Reassembly requires a spring balance and a dial guage to check the diff pre=load & backlash.   Not a particularly difficult job, but may require selective shims to get right (I just make my own out of shimstock)  

Edited August 10, 2019 by 910Esprit

[dsvitesse1]

3 hours ago, Sparky said:

Hi!  The circlip is non-critical, so no strip really necessary.  Make absolutely certain you have a nylatron washer on the shaft though.

However, I do expect some to disagree with me...

Hi, correct. Imho and for what I have read and heard before the circlip is essential. The springload is to big for the circlip. The input shaft is pushed forward and than the nylon thrustwasher will fail and input shaft starts drilling it's way into crank shaft. This issue never happens in Citroen SM or DS because bearing in flywheel is ball bearing an no nylon ring. Better install upgrade circlip.

 

cheers,

 

Harry  Martens

[David Pattison]

As mentioned, there will be some different opinions, in the interim I spoke to previous owner who had the car for 4 years and no clutch/gearbox issues.He never changed clutch or removed the box.

However I always believe it was fitted by the manafacturer then its there for a valid reason.

[David Pattison]

 

Pic of my input shaft attached - cant see where the circlip would hold, looking down the input tube there does not seem to be a ridge of sorts to hold a clip

[910Esprit]

The snapring fits in a recess in the input shaft (I mean the mainshaft in the geargox itself)  and would sit on the shoulder at the end of the splines (under spring tension) .  Thats a pretty nasty input shaft.  Maybe better biting the bullet and replace it.    I'd remove the top cover of the box and check that not too much contamination has entered via the input shaft scroll drain tube into the bellhousing  

Edited August 11, 2019 by 910Esprit

[dsvitesse1]

1 hour ago, David Pattison said:

 

Pic of my input shaft attached - cant see where the circlip would hold, looking down the input tube there does not seem to be a ridge of sorts to hold a clip

That one will end up with no drive at all soon if replaced.

[David Pattison]

If I don't fit the circlip?

[dsvitesse1]

2 minutes ago, David Pattison said:

If I don't fit the circlip?

With or without. It will fail sooner than you think 

That input shaft is toast

[David Pattison]

Picture is not a good reflection I admit,when zooming in it doesn't look great, its only a 30k car. I will have local gearbox company check it out.

This part is beyond not obtainable out here unfortunatly

[dsvitesse1]

2 minutes ago, David Pattison said:

Picture is not a good reflection I admit,when zooming in it doesn't look great, its only a 30k car. I will have local gearbox company check it out.

This part is beyond not obtainable out here unfortunatly

I have stock, incl upgrade circlip.

[David Pattison]

30.000 miles that is

Thanks Harry please quote me, delivery to South Africa

[Jonas]

I might need one as well, pilot bearing surface is shot, please quote me too Harry. S1 78.

Edited June 9, 2020 by Jonas

[Steve4012]

On 11/08/2019 at 10:39, David Pattison said:

 

Pic of my input shaft attached - cant see where the circlip would hold, looking down the input tube there does not seem to be a ridge of sorts to hold a clip

If the gearbox end of the input shaft is that worn, is it also likely there's damage inside the gearbox as well?

[dsvitesse1]

12 hours ago, Jonas said:

I might need one as well, pilot bearing surface is shot, please quote me too Harry. S1 78.

Hi Jonas, please pm or email. [email protected]

cheers,

 

Harry

9 hours ago, Steve4012 said:

If the gearbox end of the input shaft is that worn, is it also likely there's damage inside the gearbox as well?

Have to check. I make new input shafts 2 mm longer on primary shaft side.

cheers,

 

Harry

 

[ekwan]

The above drawing is from the S3 workshop manual. In the normal situation, the smaller diameter at the end of the gearbox input shaft rotates inside the spigot bearing. The nylon thrust washer does not take any "thrust" load whatsoever, even though it is called a thrust washer.

When the circlip fails, the spring force at the other end of the input shaft pushes the shaft in the direction of the crankshaft. The input shaft presses the thrust washer and spigot bearing forward and into the crankshaft recess, and as the nylon washer wears down, the end surface of the input shaft progressively bears onto the bottom of the crankshaft recess, and eventually wearing into the crankshaft.

Surely, there must be a retro engineering solution to this. I know SJ Sports Cars sell a metal sleeve that goes into the crank recess before the spigot bearing is inserted. This would prevent the spigot bearing from being pushed into the bottom of the crankshaft recess, and hopefully there would be loads of warning signs that the circlip has worked itself loose.

Edited June 10, 2020 by ekwan

[drdoom]

I had thought that the metal sleeve was for restoring the worn end of the input shaft as these will lose diameter when used for a time with a failed needle bearing. As to an engineered solution apparently the crank can be machined for the roller bearing used in the Renault boxes, done right puts an end to all the fuss.

Cheers

[ekwan]

3 minutes ago, drdoom said:

I had thought that the metal sleeve was for restoring the worn end of the input shaft as these will lose diameter when used for a time with a failed needle bearing. As to an engineered solution apparently the crank can be machined for the roller bearing used in the Renault boxes, done right puts an end to all the fuss.

Cheers

From SJ's website.......

 

[drdoom]

Right, that's a spacer, not a sleeve. 

[ekwan]

1 minute ago, drdoom said:

Right, that's a spacer, not a sleeve. 

Annulus 🤣

[drdoom]

https://www.sjsportscars.com/parts-and-accessories/A089F0404F.htm

 

[snowrx]

I wonder if one could drop an appropriately sized ball in the recess to keep the input shaft at bay in the event of circlip failure. The ball would have  minimal contact area with the input shaft at the center, so friction would be low(er) and might hold off crankshaft damage if the splines can't get to the crank flange.

I machined my crank for the later ball bearing myself, but looking at ekwan's drawing gave me the thought.

[ekwan]

On 11/08/2019 at 18:15, dsvitesse1 said:

With or without. It will fail sooner than you think 

That input shaft is toast

Hi Harry, what are they symptoms (if any) when the circlip gives way and the input shaft moves forward?

[dsvitesse1]

Hi, the spring load is so strong that eventually the input shaft will " drill " itself in the crank shaft.