2003 Explorer Sharp Turning Instability

My SUV is a 2003 Ford Explorer with ~33000 miles, has 4WD option but I've never changed it to 4WD hi or lo. It has an automatic transmission. I think it's a V6.

The problem is whenever I turn the wheels all the way to the left and continue moving the vehicle forward (while turning, like parking for example) there is this sort of jump-like motion that happens that feels like I've just ran over a small animal, maybe a chihuahua or an ocelot, that size of a jump. It only happens periodically, not everytime I turn in to park, but when it does happen I seriously think I've ran over a log or something with the drivers side wheel - the whole truck jumps and even tilts a little bit like I've ran over an object or a kitten. It's hard to describe in any other way.

Can you tell me what this might be - we're supposed to drive this SUV 900 miles there and then back this week, is it safe?

Thanks,

John