I don’t have a service diagram for the 70s Shimano 3S, but as it turns out the principles are the same as the Sturmey-Archer AW. The 3S is more compact, and unlike the older Shimano 333, the pawls are held in place by snap ring wire circlips, in much the same way as a 10-speed freewheel cluster.
This makes servicing simpler than the Sturmey Archer AW too, just don’t lose or break those clips !
The 333 must have been a nightmare with its pawl pins and hair springs, and has a bad reputation for reliability. In my experience the 3S is a good hub although the moving parts do look more delicate than the Sturmey Archer. As far as operation goes the Shimano uses a pushrod to move the gear train against the clutch spring via a bell-crank, whereas the Sturmey Archer uses the cable tension to pull out the indicator rod with the characteristic little chain helping to compress the clutch spring.
Both systems will default to high gear if the cable is detached.
I thought it best to look inside the Classique 3’s hub, not knowing its history, and I’m glad I did so as it wasn’t too pretty.
Note above – the snap ring comes off to release the 4 little cylindrical retaining pins and thus separate the planet cage from the ring gear.
I couldn’t figure out how to remove the planet gears, the sub-assembly doesn’t appear to disassemble beyond the pawls and springs so I had to flush and brush throughout thoroughly with kerosene as best I could.
I had a spare to compare it with in case I messed up, and after I finished I also had a quick look inside. This one I have owned since new and inside it looks like an Internal Gear Hub should i.e. no rust !
If these hubs can last 30-40 years without a service then if I overhaul them now they should be able to last a riding lifetime ! Just remember that you are unlikely to find spares for them at a bike shop, unless it’s a very old long established one.
If anything breaks or is lost it will probably be necessary to scrap an old hub for spares, if you can find one. The same could apply to the trigger shifter, cable and cable adjusters too, so again take care – and don’t lose anything.
I re-assembled the hub using Tri-Flow clear teflon grease and inserted a little Pressol oil down the axle after reassembly to improve the flow
I’m now looking forward to re-building one of these hubs for my Grandfather’s old Speedwell – onto a new 27″ alloy rim.
See Ya !