After the trials of the engine rebuild, see here: https://www.narrywoolan.com.au/lancia-aprilia-1070/engine-rebuild-part-one.html and the leaking rear mains seal: https://www.narrywoolan.com.au/lancia-aprilia-1070/engine-rear-mains-seal.html it was time to investigate something else.
For years my Aprilia has had a clunk in the left rear suspension. I’d rebuilt the shock absorber but that wasn’t the source of the noise. Next step was to investigate the torsion bar, t in tavola 15.
My first thought was it had been hitting on the inside of the torsion bar guide tube at the differential end, N in the tavola above. I had a perfect spare that I fitted. After a test drive the clunk was still there but I thought maybe there was a little less roll and the rear end stuck to the road a little better.
All that was left to check now was the torsion bar outer bearing, 48056. This is an odd size, 45d x 78D x 18B, and not available from regular bearing suppliers.
I wont go into the details here of removing the left side trailing arm assembly but when it was out on the bench and the bearing extracted the wear in it was obvious. The bearing is located inside the assembly at X, see above Tav 20, and relies on two leather seals, 38-74025, to keep dirt and water out, these had failed and the bearing had pitted and rusted.
Cavalitto is the only source of replacement bearings that I am aware of so one was ordered along with a pair of seals.All is now quiet at the rear. Unfortunately our Covid-19 restrictions are still in place so getting out on the road is not an option right now.