Category Archives: Suspension

Left Rear Torsion Bar & Bearing

After the trials of the engine rebuild, see here: and the leaking rear mains seal: 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.

After I extracted it the first thing I noticed was a couple of wear marks on the inner end.

And putting it between centres in the lathe it had a 0.882″ (2.08 mm) bend.

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.


Pre Castlemaine 23

October every odd year means it’s time for the Australian Lancia Register’s Castlemaine Rally. This year it is number 23.

Lancia owners around the country are sweating in their garage performing last minute fixes, some small, others almost gargantuan.

This year I tried to avoid the last minute scramble, how organised am I? As mentioned in a previous post I’d overhauled the front brakes but after the last ALR run there was just a bit too much of a whine from the differential.

On the Narrywoolan* website you can read my two previous attempts to fix the problem. This time I entrusted the magic expertise of Mike The Three Wheeler to help me set it up correctly. Taking the whole back end out for the third time was fairly easy. Stripped everything down and got Mike over to help. Sorry I didn’t get any photos of what we did but using some gear marking paste, moving the pinion in and out and shifting the shims on the diff we seemed to get a much better pattern on the gears.

Diff 2015-033

Dropping the rear end. Simple job, remove hand brake cables, top hydraulic brake line on diff, fibre coupling on prop shaft and the four sub-frame bolts!

Diff 2015-058

Diff 2015-101

I took the opportunity to paint everything and clean up the André rear dampers.

Diff 2015-076

André damper with one broken friction disc. Got a new set from the UK, cleaned all the oil and grease off, applied a light smear of SKF LGHP2 grease.

Diff 2015-183

Mike recommended trying some Red Line Shockproof Gear Oil in the diff. Once everything was back in place and a few short runs everything seemed OK. However a longer 200km trip revealed some diff noise at highway speeds and, on return, a more than normal oil leak from the pinion shaft.

Diff 2015-103

The offending leaking pinion shaft.

Diff 2015-109

Even though there is an oil slinger and a modern lip seal it still leaks down the spline end of the shaft. Anyone have a better solution??

After some head scratching and consultation of the factory manual I decided to try some Penrite Gear Oil 140. It’s a mineral oil and the same 140EP spec as the original factory recommendation. Some further long test drives and the diff is now very quiet and the leak is just small. I’ve never been able to come up with a satisfactory solution to stop the leak in the early design of 1070’s diff. Lancia changed the design later in 1937 to incorporate a better system of seals.


Just to annoy me 2nd gear has become difficult to select when changing down from 3rd but it will have to stay that way for the time being. With less than 4 weeks before the rally I’m not going to risk swapping gearboxes as the spare, although all seems to be in excellent shape, has never been run.

From October 16 I’ll be posting a daily blog on the rally.