Steering ghost

[Handmedown]

I have a 72 c10. The steering worked perfect it just leaked a lot. So I put new seals in the steering gear. I'm trying to bleed the air after putting the gear back on. The steering wheel turns fine in both directions with the tires lifted engine not running. When I start the engine the steering wheel will turn on its own slowly to the drivers side and in takes all my strength to turn in to the passenger side. What is going on? Thanks