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by George Dyke…..
I have recently seen two 2CV gearboxes lock-up and one of them was a personal experience I will soon not forget. I was out driving my Burton sportscar (a fibreglass 2-seater manufactured in the Netherlands that is based on the 2CV) and backed up the vehicle about 100 feet. As I came to a stop I heard two loud “clunks” and with that my gearbox was locked-up. It would not go into neutral nor would the car move. The wheels were locked!
Starting the car, the gearbox was engaged whether or not the clutch was depressed – it lurched forward when I tried and just stalled. And there was no way I could return the box to a normal shifting state. Eventually, with one good thrust, I managed to force it onto what felt like 3rd, but not quite
The design of the 2CV allows the top of the gearbox to be removed in situ, (a feature few other cars have) and, with some judicious maneuvering, the main gear shaft can be coaxed somewhat into a gear that will allow the car to at least roll with the clutch depressed, but you are going to hear a grinding sound and and the car cannot be driven.
In my case, it was a tow home on a flatbed and once there, a dive into the gearbox to see what had happened.
As it turned out, the collar which retains the reverse gear on the upper shaft pulled apart, (this is referred to as an unwind), thus allowing the gear to slip on the shaft and locking up the entire gearbox.
An excellent description of the problem can be found on the 2cvsrus.com website where Axel Kaliske also provides tips on how to properly reverse in a 2CV. We have re-published it below:
Never back up uphill or start very fast backing up! 2CV’s with disc brakes have a severe problem: While backing up with a high tourque, the collar for the center shifting fork twists off the gear assembly (see sketch).
The reason is that this collar was not tightened enough during production. Afterwards, it is almost impossible to tighten it more. This requires disassembling the transmission. When you back up very hard you put a high load on the transmission, which leads to friction between the shifting fork and the collar.
2CV gearbox shafts and gears – reverse gear highlighted.
The gear assembly warps and the collar twists off the thread. The collar is peened in a few spots, but this cannot stand the force. Once the collar is twisted off completely the gear assembly will pull apart. Mostly this leaves the transmission in permanent 3rd gear.
The synchro-ring twist and the gears cannot engage anymore. Maybe you can manage to engage another gear – a transmission with two gears engaged simultaneously – it will lock up. To press the clutch won’t help because it is not the motor what blocks!
A repair is challenging. In most cases, the transmission will need to be replaced. This is the reason why it is so hard to find a good used 2CV transmission with disc brakes.
So be gentle in reverse, try to avoid a high tourque. Typical situations where the transmission is threatened are steep downhill driveways to your garage or house. If there isn’t enough space at the bottom to turn around on a level surface, go down in reverse. This way you have the high tourque coming back up in 1st gear, where it doesn’t harm the transmission. Also, it makes it easier to leave the driveway pulling out forward.
Also don’t fall for the urban legend that “if you can’t make it up a hill in 1st gear, turn around and go in reverse”. This was true in the old 2CVs with 12 or 16 HP engines. In the later model 2CVs with a 602cc motor, the gear ratio for 1st and reverse gear is identical!
In my case, I ended up ordering a new gearbox from Burton. (Thank heavens they were great in responding quickly had one in stock!)
In summary, to preserve a 2CV gearbox and not