Lightweight outdrives TD310275 - too short?

[TonyM]

I just bought a set of lightweight diff outdrives 310275. The Durango website shows them to be an option for the DEX410 and DESC410 all varients.

I'm confused, when I compare them with the standard outdrive they are approximately 5mm shorter in the section that the drive shaft goes into. As my driveshafts currently only just stay in their outdrive slots I can't see how the lightweight ones will retain the drive shaft.

It's as though they have been designed for a longer drive shaft, but I don't see any as an option. Has anyone else fitted them?