Traction Avant Rear Suspension Rebuild

Another Reasonably straightforward job (for James anyway).

January 2017 - Just over 4 years into the 'Rolling Restoration' and the last main mechanical job to be done on the 52 Traction Avant is the rear suspension 'silentblocs'.

The 'Silentblocs' are basically rubber bushes bonded to metal sleeves which are pressed into housings and help to smooth out the actions of the Torsion Bars which act as the suspension springs.

Now there is no way to visibly inspect the condition of them when fitted to the car (unlike those on the front suspension) but if the rest of the bushes on the panhard rod etc. are perished then it's possible the silentblocs are as well. However there is one tell tale sign there is an issue. If you jack the car in the centre 1 of the trailing arms may drop down further than the other.

Some specialist tools are needed for the work so once again James Geddes at Traction Repairs is doing the work.

The process is explained in 'Operation 128' of the original Citroen Repair Manual (mine does) which does include diagrams and details of the special tooling required but often real life pictures help to make more sense of what is needed (and workshop manuals never expect you to have any problems removing parts!)

To replace the actual silentblocs the rear axle trailing arms need to come out, be stripped down, checked, cleaned and the 'silentblocs', rubber bushing and anything else needs to be replaced. I opted to buy new height adjusters, nuts and retaining clips as well to speed up the work. However as the rear shock absorbers were replaced in 2013 it was decided to not replace those.

The new parts once again were ordered from Jose Fransen's in Belgium.

Silentblocs What was changed Up we go

Image 1 above shows where the Silentbloc bushes are located on the car. Image 2 shows the parts which are to be changed and image 3 shows the job started by jacking the rear of the car off the ground.

There is no need to remove the whole axle assembly to replace the silentblocs as you can unbolt the housing units and they come off with the trailing arms as can be seen in the exploded parts diagram. First though you need to remove the road wheels, brake drums, shoes and backplates, disconnect the panhard rod and then the stub axle shaft.

Torsion Bars Trailing arms and torsion bars removed Heating up the retaining nuts

Image 1 above shows the trailing arms and torsion bars in place on the car, image 2 shows the unit removed and after 60+ years nothing was going to simply unscrew so image 3 shows heat being applied, rather generously...

First of the special tooling being used Retaining nut 1 removed Parts cleaned and painted prior to re assembly

Image 1 above shows the 1st of the special tools in use to remove the silentbloc retaining nuts, image 2 shows the 1st one removed and image 3 the stripped, cleaned and painted trailing arms along with the new silentblocs in the housings ready for re assembly.

2nd of the special tooling required Starting the re assembly 1st of the silentblocs fitted.

Image 1 above shows the special jig required to set the housing and silentbloc angles prior to sub assembly, image 2 shows the 1st silentbloc being fitted and the 3rd image the 1st trailing arm set up.

Rebuilt Training arm Assembly complete and refitted to the car.

Image 1 above shows a completed trailing arm ready to be reinstalled. Reassembly is basically a reverse of the dismantling. Image 2 shows the completed assembly back in the car.

Once all back together the 'ride heights' need to be reset front and rear, fortunately the front adjusters were cleaned up last June when the Front Suspension was overhauled so that job was relatively simple. Others haven't been so lucky.

Whilst reading the above guide takes a few minutes, the actual work took circa 20 hours to complete by someone with expertise and knowledge. Yes with the tooling a competent DIYer could tackle it, but it could take considerably longer.

October 2017 - Adjusting the weight Distribution

When the rear suspension was rebuilt James set the 'ride heights' to the tolerances specified in the Workshop Repair Manual however the opportunity arose to carry out a 'Weight Distribution' check using a set of scales normally used for setting up race cars!

Now Citroen did make a set of mechanical scales (part 2310-T) but those sets are very rare and so not available. However we know that the front suspension arm was bent and bearing in mind the cars age and unknown past it was a worthwhile exercise to undertake.

The workshop manual is quite specific when it says 'THE LOAD DISTRIBUTION OF EACH WHEEL IS OF GREAT IMPORTANCE IN THE MATTER OF ROAD HOLDING, BRAKING AND TYRE WEAR' and 'Load distribution is of greater importance than body heights under the hull'

When James checked his own car (which had signs of being hit in the past on the right front) it was well out of balance according to Citroen data.

Mine today wasn’t too bad but there was still over 35kg difference (the specified tolerance in the workshop manual is 30kg) across the axles so it was adjusted a wheel at a time.

Traction Avant Weight Scales Part Number Weight Distribution and load balancing completed figures.

It ended up at 8kg difference across the front and 6kg across the back as shown in the image on the right so whilst not entirely balanced well within tolerance. Now no figure is given for front to rear weight distribution however given all the weight of the engine and gearbox at the front of the car, a load difference of 11-12% front to rear doesn't seem to be not far off at all for a 65 year old Car:)

Does it actually handle any better?

Well I only had a 5 mile drive home but yes, it did feel more stable in bends at speed.

Overall driving the car now feels much smoother and more stable when cornering and what the car would have felt like when fresh from the factory.

Last Update: October 2017