GrandePunto PL said:

He's probably talking about the gearbox itself.
Housings of the gearbox bolted together result with input shaft resistance. This could be a small misalignment, I mean some parts (bearings) are pressed into the shafts more or less deep, that's what's making the shaft harder to turn.
Unless it's a real mistake, significant f-up during assembly, it should fix itself the moment car is started and put into gear.
The small resistance to turn by hand can be actually desired, good thing (depends on the design, type of bearings etc.).

PS
Remember kids, don't start the engine without axles installed into gearbox. You can blow up the differential casing.

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