Fun fact: Since 2001, Sturmey has fitted the AW-NIG/SRF3 with the HSA440/HSA621 one-piece forged axle with integral sun gear (axle interchangeable with the AW). This is the part you get if you source a spare for repair. The Sturmey Intelegencia considers this to be an upgrade as it is more durable.
The Axle for the s3c is different than the AW to be able to fit the coaster brake in the hub. All the gears are narrower which makes it easier to strip teeth off the sun gear. I've hammered on some AW hubs and never had issue with them, but I am also not a big guy, 160 -165 pounds typically.