Traction Avant: Upgrade to 4-gear gearbox

Installation of a Citroën ID/DS 4-speed gearbox in a Citroën Traction Avant

Here you can read how I discovered the best way to equip my Traction Avant 11BN with 4 gears, due to damage and shame.

The Citroën Traction Avant has originally 3 gears of which the first gear is not synchronized.

In my opinion this gearbox is the biggest problem to drive this car in modern traffic.

From 2007 to 2016 I have worked intermittently on the adaptation of an old Citroën ID/DS19 4-speed gearbox to work in my Traction Avant 11 BN.

As basis for this project I used a Citroën ID donor gearbox from a 1964 Citroën ID19.
The ID 4 gearbox has full synchronization on the 4 forward gears but doesn’t fit in the available width of my Traction Avant.

The process of alterations and adjustments to the ID gearbox and the installation in my Traction Avant is shown in this post, added with an attached photo collage!

Above you can see the rough end result with which I have already (2018) been able to cover a few thousand kilometers.

In the end it was a very rewarding and valuable project.

Driving the TA is now perfect, shifting back and up is smooth and the car behaves nicely.

An important advantage of the new gearbox is that the engine makes much less revs when driving at cruising speed.

Above you can see the overview of the donor longstroke ID19 engine with the 4-speed gearbox.

At the time of purchase everything was still attached to it: brakes, suspension, gearbox, HD controller, petrol pump, alternator and so on!

The water pump had already been removed by another person.

The picture above dates from the beginning of 2009, after disassembling the combination engine and gearbox of an early demolition – Citroën ID19 with long stroke engine and 4-speed gearbox.

The approach

The long flanges of the 4-gear box must be removed, the ends of the flanges (side of the gearbox) must be turned to fit the bushes that will be placed in the turned flanges. This is necessary because the bearings and seals are not available in outer dimensions that simply fit into the inside of the shortened flanges.
New bearings and new oil seals are locked in the bushings in the turned flanges.

The axle end ‘claws’ are turned down with approx. 1 mm to a commercially available inner dimension for a bearing and barrier. (35mm shaft thickness)
The flanges are machined down with 3 mm in order to be able to mount the ash claws on the TA internal gearbox shafts.

A stainless steel bushing is rotated to tighten the outgoing internal TA-axis in the ID crown wheel. In other conversions this bus is usually not placed, but the lateral pressure at the end of this shaft is without pass-bus to my view too large to be able to drive for a very long time without wear and tear. The bus has an oil groove on the rotating inside. This bus is needed on one side of the donor ID-crowned wheel and is tightly shrunk in the crown wheel. The ID-axis rotates tightly in the ID crown wheel and is slightly thicker than the TA-axis. The difference in thickness is corrected by the stainless steel pas-bus.

In addition to the solution as described in the above article with corresponding picture above the article from Robert Williams CLICK FOR DOWNLOAD, I added single ball-bearings as far as possible to the right in the above picture, just like the ones that are used in the original ID situation.

The TA’s satellite wheels, internal axles and differential housing are reused.

The satellite wheel (of course matching the pinion cog of the ID box) comes from the ID donor box.
After the conversion, you will have to determine the preload on the Timken bearings again and make new fit rings in order to mount the whole with the correct preload in the ‘clock’.
Measure the play of the crown wheel according to the workshop manual, and so on.
This solution is robust and will not break or wear out excessively. Operating the gears was also an important point for me, because the Traction Avant has a different shift sequence as standard and the well-known ‘conversion’ to a 4-speed gearbox all have an extra button or lever to control the reverse of the gearbox. I chose to rebuild everything in such a way that a regular H-fork 4-speed + reverse operation is created:

  • via the original shifting rods of the TA
  • by converting the selector/levier into the cabin
  • by converting the control levers at the bottom of the gearbox to the original operation of the 4-speed gearbox with new shifting rods ‘outside’.

Removed the gearbox external shafts and continued working with the flanges.

Above you can see how I am turning the bushings for the flanges, in which the new bearing and the new oil seal will be mounted.

Here the heart is removed from an old ID-19 clutch plate to serve as an extension of another matching plate. For ease of use I used a new TA plate, an ID plate is also possible in principle but then the keyways have to be in line with each other so that the plate can slide freely over the primary axis. This action is necessary because the primary shaft of the 4-bucket is shorter than the shaft of the 3-bucket and the keyway of the shaft is just not far enough in the keyway of a standard clutch plate to transfer the force to the plate without damage.

On the picture above it may not be clearly visible, but the bushings are locked to the flanges with stainless steel screw/spikes so that they can’t move and/or turn. Then the flange is turned on the outside to make room for the convex protruding parts of the 10mm threaded ends of the shaft claws.

Here the flange, in the above picture, was not yet turned down.

In order to fit the bearing caps, they are very carefully turned out in counter arrangement in the lathe to the size of the Timken bearings.

Above you see a reworked flange with bushing, oil seal and bearing, mounted between gearbox and clutch housing.

Next job: Extend the drive shaft to the pulley of the ID motor. The extension of this shaft was necessary because at the same time as mounting the 4-speed gearbox I built in a longstroke ID motor. The end of this drive shaft towards the crankshaft is slightly thicker than on the Traction motor and the shaft is slightly deeper embedded in the ID-motor. See the picture below where the already prepared TA-axle is above and the ID-axle is lower.

Top: Extended custom pulley shaft ready for mounting

Above you can see the heart of the ID clutch pad with ID keyway of a demolished clutch disc mounted on a new TA clutch disc. The welding is done with the specially made fitting rod I made to adapt from ID to TA sizes and it is tightly pressed into both keyways. This bushing is only removed after it has cooled down completely . To ensure good adhesion, the welding work was first done with CO2 and later grounded out in 3 places, the sleeve was put back in place and welded again with MIG. After that I had the welding checked for swings of the new keyway in relation to the clutch plate. Luckily that was well within the standard aceptable deviation.

Above you can see the required fit & fill plate made of 4mm thick aluminium with which I performed the 100% fit of the TA-bell housing to the ID-gearbox. The advantage of this solution is that the satellite housing also runs neatly free from the inside of the clutch bell housing and you don’t have to worry about a possible differential running against the clutch housing.

The reason for this necessary adjustment is the fact that the position (in the longitudinal direction) of the drive shafts on the TA in relation to the ID has just shifted 4 mm. The semi-circular recesses where the flanges fit the id gearbox and where the original oil seals fit the TA beel house are not equal to the ID on the bucket side versus the side of the clutch housing.

The shape of the original TA setup is exactly the same on both sides (bell house and gearbox side). On the ID body the hole for the flange is 4mm shallower on the bell house side and 4mm deeper on the ID gearbox side. With a fitting plate between the ID gearbox and the TA- bell/coupling housing, the non-circular shape is compensated by adding 4 mm so that the pure round flanges fit exactly into the (again) round hole. 

I had to completely adjust the levers of the gear control on the underside of the shifting tower so that the newly developed rods can be operated for the ID gearbox. It took some thinking and trying but this solution works fine! As you can see on the picture, the ID pulley only fits just next to the right lever. By using this pulley I obviously had to switch to a narrower V-belt. That meant an adjustment of the water pump pulley, and the assembly of a 12 Volt alternator.

Above you can see the 4 mm fitting plate in detail. For the final assembly I used thin paper gasket on both sides of the passport plate. That turned out to be the only way to get everything put together leakproof.

The shifting rods between geartower (left) and gearlevers (right) to the selector in detail: A small extra challenge for me was that the carburettor, by placing the ID engine and the corresponding cylinder head, suddenly ran in the orbit of these shifting rods. With a water pipe bender I was able to keep the shifting rods exactly free of all fixed engine parts and it all fits just fine.

The gearbox without control rods mounted on the clutch housing. If you look closely, you’ll see that I still worked here with the original ID gearbox shafts, which I had shortened. In the end this solution didn’t work because the welded shafts would always break at the weld. Basically this solution is possible, but then you would have to make new shafts (or have them made).]

Above you can see the elongation of the primary axis by means of a bus that connects to the primary axis. This bus comes between the primary axis and the top bearing of the engine’s crankshaft. The aim is to prevent the primary shaft from swinging. The bus on the picture was my prototype. There appear to be top bearings with different inner diameters in which the primary shaft fits and so here also, the practice was (again) my teacher.

Clutch plate in the (flush mounted) attachment ring of the newly installed diaphragm pressure group

And the entire pressure group with the clutch plate mounted and the protruding keyway of the clutch plate.

Coupling /bell housing with M10 bolts for securing the flanges. The M10 bolts are mounted through and through in the sidewalls of the housing. Earlier I experimented with other solutions but with threaded taps, bushings and the like I couldn’t get it sufficiently oil-tight. In the above way with rings and gaskets it is perfectly sealed!

This was a bit of a job: Making 1 new differential from donor parts of 2 differentials. In itself not difficult when you think about what will fit into what: Pignon of ID has been applied, so the satellite cog of ID has to be applied. The output shafts of the TA are used so the satellite gears of the TA have to be placed. The thinner output TA axis is placed in the satellite gear of the ID so a pas-bus must be pressed into the ID satellite wheel so that the TA axis can rotate freely but tightly in it. The Satellite housing of the TA is used (bowl-side where the gears are located) with the fixed (TA) axis attached to it. In the picture above you can see the satellite sprocket with free rotating output shaft in the lower left corner. In the lower right corner you can see the com-part of the satellite house with the satellite sprockets and fixed output shaft. The original TA differential works with axial shafts with keyways on the outside on which the TA shafts can be mounted externally. The advantage of this is that you can easily replace the large retaining rings of the TA body. In the picture above, the lower differential is the TA differential.  

Top: Ready and mounted differential. The fit in between bus is a good fit.

Above you can see the made fit-in between -bus with oil groove on the freely rotating inside.

Timing bearings tight but not too tight…

Converted switch selector/levier, in the experimental phase.

Turning the axle end ‘claw’ towards the commercially available bearing size

And the result.

Mounting bracket. I opted for a very robust design, because the motor/body/drive axles are all suspended from this point. Moreover, I have chosen to simply re-assemble the transverse parts of the drive unit to keep them strong enough.

Pay attention to the above: On the underside of the flanges I have grinded away about 2 cm of material on both sides. This is because these points protrude from the original TA gearbox. This brings them to the TA- cradle just above the passage of the drive shafts. So I had to remove some material. The number of times that I have mounted and disassembled the gearbox I can no longer determine, but it was at least so many times that I can now do it blindly and very quickly.

Above: Shows the removed material of the gearbox’s flanges: Handy to do before mounting!

Bearing for the axles-ends ‘claws’. I heated this part in the oven to 60 degrees for final assembly.


Switch shafts. Left the movement up/down of the hand lever and right the movement left/right…

I had to unload a stub axle on one side, otherwise I couldn’t get the axles mounted on the bogie axles (flanges).

Taken during assembly: tighten the nut and so on. On the right you can see the transducer of the cruise control hanging away. The magnet is placed under the nut that is still loose with a bracket so that the recorder can see it at every turn.

Above the adapted levers of the underside of the switching tower.

And- the final assembly!

And-all available photo’s related to the above topic:

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