Esprit Gearbox Circlip Issue

[NeilP]

What’s the experts view of this car? Wasn’t there a topic relating to gearbox / circlip and float which needs careful checking (?) 

https://www.pistonheads.com/buy/listing/16970681

[Fridge]

Relates to the Turbo Esprit, not S1. One of those continuing old wive's tales along with 195/70 front tyres that keep being perpetuated.

[910Esprit]

The circlip issue is not something that keeps me up at night.... However, I cant see why it would only affect Turbo Esprit's but not any other G car  I cant think of a single material difference in set-up - They both use identical spring loaded input shafts, secured by a flimsy rust prone circlip, bearing against the end of similar crankshafts, insulated by a nylon washer - Is there something I've missed?

[Fridge]

The story goes something like this (it's well documented)...

When the Turbo Esprit was being developed Lotus were concerned that the increased dynamic forces exerted by cause stress on certain components. Partially, as I understand it, due to the square profile of some components. In particular the area around this part of the transmission. Which was developed to prevent possible failure.

This situation does not exist on the earlie, less stressed cars. Though some owners still fret about it.

Check it out.

[Fridge]

39 minutes ago, 910Esprit said:

The circlip issue is not something that keeps me up at night.... However, I cant see why it would only affect Turbo Esprit's but not any other G car  I cant think of a single material difference in set-up - They both use identical spring loaded input shafts, secured by a flimsy rust prone circlip, bearing against the end of similar crankshafts, insulated by a nylon washer - Is there something I've missed?

I've done the work for you.

Tim Engle's explanation:

The Nylatron washer doesn't last for ever, it does wear.   And as it does, the input shaft moves forward.   The early naturally aspirated Esprit's input shaft had a square shoulder that got a very solid bite on the circlip, and having the input shaft get past it is rare in those cars.

The 910 Turbo's greater torque pushed the Citroen trasaxle to it's limit, so parts were massaged to remove sudden transitions that could be stress concentration points.   One of those changes replaced the input shaft's shoulder with a taper.   The tapered input shaft can get past the circlip as the Nylatron washer wears, and it's the Turbos that experience the vast majority of the escaped input shaft problems.

Even in Esprit S1-S2 with square shoulders, in which the input shaft never escaped, I've found the Nylatron washers worn down to almost nothing.

I agree, as long as everything is right, and the Nylatron washer is full thickness, the input shaft is pressed back into the primary shaft spline, and there's no pressure on the circlip.   I never said that wasn't the case... please be patient and only hang me for what I do say.   😞   But when the input shaft gets free, and they do, it's because everything is NOT all right.   In that case, the little OEM circlip is not capable of being the back-up that saves the day.

I've seen several G-Turbo input shafts that have cut their way about an inch+ into the back end of the crank, until the splines between the input and primary shafts disengaged to the point that they couldn't transmit the torque, and they stripped.   No more drive, both shafts toast, and the crank has to go to a machine shop for repairs.   A more robust circlip/ snap ring would have prevented that..

The 'Heavy Duty' snap ring that is available from Harry Martens and JAE is still very small... barely a noticeable improvement.   But it is an improvement, and it's much more secure.

Regards,
Tim Engel

[910Esprit]

Hmmm - Thanks for that David - Although the originator is a well respected commentator, I'm not convinced...   (Has there ever been a case of a G car shearing the input shaft? )   I've dismantled more of these boxes than most people and I've seen maybe 3 where the circlip has failed - and its always through a combination of rust and fretting that wears it away 'to nothing' until the shaft pushes through the remains of the circlip.   Based on your earlier thoughts, the only thing I can think of is that the increased torque of the Turbo, will eventually increase wear through the increased amount of radial load and corresponding rust/wear/fretting in the splines - which is always evident.   And presumably more so than an NA

[Fridge]

29 minutes ago, Fridge said:

One of those changes replaced the input shaft's shoulder with a taper.   The tapered input shaft can get past the circlip as the Nylatron washer wears, and it's the Turbos that experience the vast majority of the escaped input shaft problems.

☝️

[910Esprit]

Well I'll be zipping about near your Gaff tomorrow in my 115k Turbo - Zero concerns about 'tapered shafts'  or worn Nylatron washers as I'm popping and crackling on overrun down from Catnab.

 

[Fridge]

You will be if descending Saltburn Lane to Catnab. It's the steepest road I've cycled for many years, and I've toured in the French Alps. I can barely run up it after my "gym" session along the beach.

[Andyww]

11 hours ago, 910Esprit said:

Hmmm - Thanks for that David - Although the originator is a well respected commentator, I'm not convinced...   (Has there ever been a case of a G car shearing the input shaft? )   I've dismantled more of these boxes than most people and I've seen maybe 3 where the circlip has failed - and its always through a combination of rust and fretting that wears it away 'to nothing' until the shaft pushes through the remains of the circlip.   Based on your earlier thoughts, the only thing I can think of is that the increased torque of the Turbo, will eventually increase wear through the increased amount of radial load and corresponding rust/wear/fretting in the splines - which is always evident.   And presumably more so than an NA

Spot on.

I have first hand experience of this having replaced my input shaft and primary shaft and last time I was at Lotusbits I sat down with Mike and we discussed it over coffee.

The tapered shaft is an old wives tale, all the shafts are the same and are Citroen parts. Hence the weird clutch friction plate which has an odd number of splines.

The issue is caused by these factors:

Moisture gets into the circlip area and corrodes the clip and both sets of splines, input and primary shafts. The clip gradually fails. 

Each time the clutch is engaged, the clutch plate will tend to pull the input shaft by a small amount but normally if the clip is intact it will be reset each time.

When the clip fails this movement momentarily presses the shaft against the nylatron washer. The force is high because under load the clutch plate splines are under load from acceleration so will grab the input shaft. The issue is made worse if this washer has been replaced by a black one from certain suppliers which are not hard enough. The OEM Citroen washer is white and is a very tough solid material with a hardness similar to steel. I think the suppliers areconfusing Nylatron with Nylon.

The washer disintegrates and allows the shaft to grind into the crank. The repeated force of clutch actuation, under rotational load, will apply a gradual ratcheting action over time which will push the spigot bearing into the crank.

Owing to the aforementioned corrosion of the input shaft/primary shaft splines, and less spline engagement, in severe cases the splines can fail losing drive but this is rare.

In my case I caught it because I heard a noise and knew what it was so it only ground a tiny chamfer in the crank. The washer remains were in the bottom of the bellhousing. The splines on the input shaft and primary shaft were so worn I had to replace both. Its possible I might have got away with leaving the primary shaft but didnt want to risk it.

Counterboring the crank and fitting a proper bearing should also prevent this (as on Citroens). The standard needle roller bearing has no inner race so all the friction is applied to the washer if this happens. With a ball bearing the inner race will turn hence no friction. Fitting a spacer behind the standard needle roller bearing will not prevent damage if the circlip fails again as the shaft and washer will still be bearing onto the fixed outer race.

There is an oddity about the Turbo clutch which might explain why this happens more on the Turbo, which is the bellhousing has a design flaw. The pivot of the clutch fork is located such that the fork presses off-centre on the release bearing (which is why some aftermarket release bearing assemblies break). That might cause more movement and grabbing of the plate on the input shaft when clutch actuated. Other than that its not really clear why this only happens on the Turbo. Maybe the larger clutch also make a difference.

 

 

[snowrx]

Here's what my clip looked like when it came out of my turbo. Car had 60K+ miles on it and came with a worn input shaft in the spares that had already been replaced. Regardless of failure mode, boring the crank for a later stye roller bearing seems prudent when the crank is out.

[TomE]

Moderators - this is really useful info.  Can it be copied into its own thread (or a relevant existing one) so it’s easy for people to find in future?

I appreciate it’s also an important point for people looking at used cars, so has relevance here. 

Thanks for the inputs from knowledgeable folks. I’m going up a steep Esprit learning curve at the moment!

[Andyww]

2 hours ago, TomE said:

Moderators - this is really useful info.  

Its probably the most important info there is, on Turbo Esprit with Citroen box because it will eventually happen to all cars. The symptoms are a grinding noise momentarily when the clutch pedal is being released. If this happens the car should not be driven, to save the crank.

The bare minimum would be replacing the circlip which means removing the gearbox then taking off the bellhousing. In most cases it would be worth replacing the input shaft as well. If the primary shaft needs replacing thats an entire gearbox dismantling, as the primary shaft is the last part to come out. This is what you end up with on the bench, the primary shaft can be seen still splined into the input shaft at the top. The primary shaft has 3 gears integral with it and is very expensive.