- The complexities of a rear gearbox ! - 

How can you improve on a 2CV ? Many people have tried and some of the creations have been excellent and some you have to see ‘in the flesh’ to really understand quite how interesting they can be.

One of the classic modifications made by Citroen themselves was to put a gearbox and engine where the boot was and call the car a Sahara. Can a Sahara be improved on ? Well if it is like mine you would think so as it has two ‘twin-pot’ Visa engines connected to standard 2CV gearboxes. That’s 37 hp at each end instead of the original 12 hp.

My technical colleagues tell me that the Visa engine is somewhat better even than the 602cc 2CV engine as it has the following qualities: Electronic ignition, a three bearing crankshaft, teflon lined barrels and is a massive 8.3% larger in displacement at 652cc. The electronic ignition needs a little care and absolutely must be well earthed and the others I take as read not having looked inside either of the two engines fitted to my car.

The one archillies heal of my car is the rear clutch. Citroen originally put hydraulic clutches (which have proved difficult in themselves) into their Sahara but mine had a cable clutch for which I carried three spare clutch cables due to a number of breakages. The other issue to be overcome is the joining together of the Visa engine and the 2CV gearbox. They join well but the ‘ring gear’ on a 2CV flywheel fitted to a Visa engine does foul on the inner casing of the 2CV gearbox bell housing. There are a number of proven ways to ensure that fouling does not occur.

My car had 3mm spacers between the engine and gearbox to ensure that the flywheel didn’t foul the bell housing. This had to be matched with a similar spacer in the middle of the clutch thrust bearing to ensure full disengagement of the clutch when the one pedal is operated. One other way, which we liked and embodied was having the flywheel milled to enable the ring gear to sit 6mm nearer the engine and so remove the need for the 3mm spacers between engine and gearbox and the spacer in the clutch thrust bearing. There is an excellent web site, which tells you just how to do this at Cats Citroen

The flywheels were milled to enable the ring gear 6mm nearer the engine all for a few cases of beer. The next step was to fit the new flywheels, take the spacers out of the thrust bearings, adjust the electronic pickups to ensure they are in the same relative position on the flywheel they were before and offer up a prayer.

The clutch operating mechanism (the long cable) needed to be modified to take a standard 2CV clutch cable at each end with a solid metal rod in the middle and this was the winter project.

On 19-October-2002 I took the front engine out of the car (the front engine being much easier to work on than the rear one and easier to view if something doesn’t look right) to fit the new milled flywheel and a new clutch.

It was quite a long job (about two hours) to get all the electrics disconnected and the engine out and the new flywheel and clutch were fitted without any problem. The engine was then placed back in the car and mated to the gearbox. When drawing up the nuts that secure the engine to the gearbox careful note was kept of the position of the flywheel to ensure that all the previous calculations were correct and that the flywheel did clear the 2CV bell housing. It did so. The next job was to carefully turn the engine over whilst listening intently for any noises that emanated from that area. There were none. The electronic ignition cradle was then fitted and the high and low speed pickups screwed into position. Again no interference with the flywheel was noted. The engine was turned over again and the area around the flywheel flooded with light. Yet again everything worked as planned.

It was decided that a quick ‘run’ of the engine was appropriate at this stage so electrics were connected and the starter button pushed. The most appalling noise came from the area of the starter motor and flywheel. We recalculated the measurements and although it appeared the throw of the starter motor bendix was not great enough the calculations proved it was. Then the fix dawned on us that we had made an assumption that the ring gear on the car before we started work was Visa and it was highly likely that we were trying to get a 2CV starter motor to drive Visa ring gear. Some careful counting proved this to be the case so the next job was to take the engine out (a five minute job this time – just six nuts and bolts) and change the ring gear over. A quick run around with a hot torch and judicious hits with a soft-faced hammer and the ring gear will come off amazingly easily.

The engine was removed; the 2CV ring gear fitted, and refitted quickly but there was a knocking every revolution. It was engine ‘out time’ again and it was noticed that the electronic pickup on the flywheel stood slightly prouder of the flywheel than on the other flywheels we had. A few judicious thumps with a hammer pushed the pickup slightly further into its housing and it was ‘engine in’, electrics on and a sweetly running, if somewhat noisy engine with no silencer fitted. Having learnt ‘all’ the tricks on the easily accessible front engine, where you can actually get your eyes into a position to see the pickups, the same job had to be undertaken on the rear engine.

In the meantime the prime objective of this work was to get the rear clutch to work. It’s clearly a good idea to try where possible to use standard Citroen parts (especially the ones that may need replacing in the future). The plan for the rear clutch was to use a standard 2CV clutch cable at the front and the same at the rear and connect the two via a 13mm x 13mm piece of square section steel. The front part of this proved to be a little difficult, as we had to get the clutch pedal, (actually two clutch pedals welded to make one) to pull two cables. Then we had to manufacture an assembly to allow the front clutch cable to bear on something so it could exert a pulling motion. This actually proved quite easy, as the gear lever mechanism is an old gearbox casing. The rear clutch cable was simply attached using all the previously installed hardware. The two cables were connected using the solid metal rod. To do this I had to remove the two petrol tanks (one under each front seat – just think for a moment that the space used by a standard 2CV fuel tank is full of engine, gearbox and exhaust so it’s not the most suitable place for highly inflammable fluid).

It looked as if the rear clutch would work but it could not be tested until the spacers were taken out of the rear engine. This was done and the modified flywheel fitted. All looked just fine until we discovered that the solid rod was actually 45mm too small. The rod was lengthened and everything looked fine until it became obvious that the small modification made to the rear clutch cable (there are two and this was the one at the back of the car) wasn’t pulling the clutch to the disengaged position. It turned out after much thinking that the outer of the clutch cable should be longer so we fitted a non-modified clutch cable, refitted the engine and it all looked very good. The car moved forward when the starter is engaged and in gear (rear gearbox only) and didn’t move at all when in the same state with the clutch disengaged.

I only needed to put it back together now !

The exhaust for the rear engine has to be seen to be understood and it took a little time to get it back together. I discovered that new exhaust clamps work wonders ! Once back in and with everything connected we were able to attempt a start but couldn’t seem to get any fuel through. I learnt a new trick here, which was to attach a new fuel pump to the end of the fuel pipe and manually pump. This works very quickly and saves on battery and starter motor life. Very shortly after that the rear engine burbled into life and that just left the bits and pieces to be fitted to the front engine and the interior of the car to be reassembled. A five-minute job – sounded like it but there was at least six days work for me.

After this we just couldn’t get the front engine to start. However after a few minutes of head scratching we found we could get it to run quite fast but it just wouldn’t idle at all. A Visa requires 12 volts to the carburettor to keep the slow running jet open and it just wasn’t getting that 12 volts. So the engine would run, but not idle and as Steve’s premises were somewhat full I decided to take the car back home.

A few weeks later I had the time to look into this idling problem. I discovered that the wiring loom should have run down the offside of the car instead of across the car and under the air filter as is usual on a 2CV. This made the wiring look very different and much easier ! The front engine then idled as it should.

Saturday 1-February-2003 was a red-letter day. The car was polished and I took it out for a short drive running on both engines. It really is such a nice car to drive and the clutch pedal requires only about 50% of the pressure previous required.

The tidying up of the car took three weekends so my estimate of two days was wildly out.

During the rebuild of the clutches I washed the seat covers and found that the fact they were 10 years old and had been subjected to some very damaging Australian sun suggested new covers and so new seat covers and door panel covers were ordered from Matthew Damper. I was very lucky to find a colour in Matt’s range to match the Sahara colour.

The MOT was passed on 9-February – some three months ahead of schedule which means that I can now renew it in the middle of the winter and if it fails I’ll have the time to fix it !

So many people have said they intend to build a twin-engined 2CV and ask me what my views are. Not having built this car I can’t comment but I am always happy to tell them how much time goes on maintaining this car ! Other people I have spoken to just give them a one word answer – don’t !

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