Is there any problem with re-filling an 8.2 rear housing with the cover off while it is out of the car?
How would you fill it with the cover off? Install the cover and fill it as normal through the fill plug until it just runs out.
With the cover off and the opening straight up. Put the fluid and additive in, put the gasket on and the cover back on.
Basically,I filled one until it dribbled out the fill hole,then I pulled the cover and drained into into a measuring container to get the amounts for different rears. Some special covers will allow more fluid. It's just easier for me to fill it with the cover off,as I can pour it all over the gears and unit,to give everything a good coating,then seal it up with the lid. I have them on large stands,with the pinion pointing down.