Pinion nut too tight?

Hello everybody,
I've purchased an original brand new diff (old stock) for my Series SWB with Rover axles.
I've noticed, before installing it, that was almost impossible to turn the pinion without a great amount of force applied.
So I proceeded to slacken the pinion bolt and everything turned without problems.
When I installed the diff at the rear axle, I re-installed the pinion nut and torqued it to the correct amount found on the green bible (130nm). After that I wasn't able again to turn the pinion without applying much force.
Now I'm worried that too much strain on the pinion bearings is applied, and also I notice a pitched vibration when accelerate or decelerate from 40+ mph.
Don't want to destroy this brand new diff!
So, it is normal that it is almost impossible to turn the pinion at hand?
Or I have to slacken the nut and let the diff rotate without drag, although at a lower torque value of the nut?
Pretty confused...

130nm seems far to high.
My manual says 70 to 120ft/lb

if its too tight when pinion nut is tightened it needs a thicker shims between pinion bearings or spacer is missing from behind flange, once a nut is tight extra torque makes very little difference

Have you got a workshop manual? It lists the various shims' to use.

Thank you all for your replies. I hoped that a brand new diff (although old stock) didn't need to get adjusted!
So if I have to add shims it means that I will have to take the diff off the car again? Or it could be done only taking off pinion nut and oil seal?

you need to find why first, but youd need to remove seal and outer bearing to change the shimming,it would be trail and error to get it correct so you wouldnt fit seal till it was right

Can you get it exchanged by whoever you bought it from?

Unfortunately no way to send back as it came with the Land from previous owner..

So it is at least a great thing I have not to dismantle again everything.. to extract outer bearing is needed special tools or it should slide out easily?

telescopic magnets are good one each side ,you wont be able to set rolling resistance properly but flange should have no play at all and a slightly tighter feel once nuts tight, so you can feel that the bearings are loaded slightly, it should rock easily by hand without feeling loose