Originally Posted by
Duragrouch
I think I see what you are saying; having two modes engaged at the same time. I hafta think they designed in more tolerance than that. I recall on my Shimano 3, if I didn't let up in pedaling hard, it would just stay in that gear, and the moment I let up any pressue, it would shift.
Hopefully the problem is just the cable out of adjustment. Next worse, needs flushing and lube. Next, pawl springs/pins/pawls, or planet gear pins. Worst would be serious damage due to rust or other.
At one time, Germany (OP location) was one of the countries on the trilateral commision of internal gear hubs, the others being the UK and Japan. EDIT: That was someone else. This OP is in GB/UK. I hope repair for them is still easy to find.
All Shimano 3/7/8 speed IGH hubs REQUIRE that you stop pedaling when shifting. It's well known that the hubs geats get damaged if you shift under load/whilst pedaling. I own all 3 hubs, and that's the ONLY requirement that must be religiously followed. Even the 3/5/8 speed Sturmey-Archer IGH hubs require you to stop pedaling or face the risk of DESTROYING the hubs gears. I've owned all the IGH hubs mentioned. My NuVinchi hub was the only one that was "supposed" to be able to be pedaled under load. It wasn't what it was supposed to be. It was a PITA. LoL!!!
Now, what you "think" might be the case isn't relevant. These hubs break when they're used incorrectly. My oldest son almost killed my BOMB-PROOF Shimano Nexus 3 speed IGH riding up hills SHIFTING!!! After I "reeducated" him about its usage, I'm happy to say that it's over 20 years old, still rockin', and I haven't bothered to have maintenance done on it yet. Some day. but no time soon.