Cargo Bikes

Ah I see.

Bosch's stated policy is they support systems for 7yrs after they've been discontinued, but Gen2 has only recently been discontinued so we'll see how it pans out.

They did release a pretty in-depth service kit for Gen2 DUs that looks pretty promising. It's about $125USD retail and replaces most of the internals as well as the entire drive side of the DU including the chainring splines and lockring threads. I haven't done one yet, but looking at the procedure, my guess is it'd take about 60-90min to perform a DU overhaul.

As far as upgrading aftermarket, the biggest issue is that Bosch doesn't generally sell DUs unless they're a replacement for an existing one. So upgrading to a completely different DU isn't really an option.

But assuming you could get a DU, Gen4 is it's own standard, but the frame fitting for Gen2 and Gen3 DUs are the same. The latter uses a standard chainring however and a lot of the bikes we've seen transition between model years have had their frame designs altered to accommodate this, so an upgrade from Gen2 to Gen3 isn't always possible due to chainring clearance issues.

We did see an interesting adapter on a Moustache tandem that allowed them to fit a Gen4 DU to a Gen2/3 frame that was pretty neat, but it doesn't appear to be available aftermarket...