Help Needed With Transfer Case
 

Ok guys picked up an NP236 (4 Button) Transfer Case for $70 from a rolled Blazer with 80,000 miles on it. Only problem I could see it was drained DRY, it was in 4HI to begin with but I couldn't get it to shift (tried with a 9/16 wrench). I figured it was because of no fluid so I filled it with oil (GM Fluid). After spinning it by hand for a while and turning it upside-down ect. I can get it to shift from 4HI to Neutral then to 4LO with the wrench, but I can not get it to shift into 2HI. I'm wondering if anyone can give me an idea of the problem is with out having to take this stupid thing apart. Could it just need to spin at a higher speed to get the fluids in all corners? It was so dry there wasn't a trace of any oil on either the drain or fill plugs they were perfectly clean. I might try to hook up an encoder motor and jump it with a ski-doo battery and see if it just needs more torque, I used to do that with my Bravada when the AWD kept blowing fuses. Any input is highly appreciated, thanks. And yes I HAVE looked for info on here related to my problem but everyone else has their transfer cases attached to a vehicle, I don't.