Just picked up an 03 Disco and noticed a steering wheel shake. I got new tires, an alignment, and a rebalance. Not sure what i should check/replace. any ideas?

 

Lots of ideas here on the forum. Do a search for Death Wobble.

Basically involves replacing bushings and tie rod ends and tightening up the hubs.

 

Check the joints at the ends of the two steering rods (the drag link and the track rod), commonly called the tie rod ends.

 

It may be worth putting the front axle on stands and try to move each wheel back and forth to determine where the slop is. Depending on the mileage, replacing the aforementioned parts may be a requisite next step.

 

Once I found that a rusty/stained/dirty spot* on the brake disc caused that wobble. Power wire-brushing it cured the shake. [check all 4 both sides]
Another time was for oblong/obround new tires that were well balanced twice. Was not about tie rod ends nor alignment nor bushings nor bearings wear. Tires were replaced by warranty. Tires with flat spot from long sitting cause that too !

* Actually was from a seagull well aimed on-target aged (corroded) 'aerial bombarding !' Clues provided at the rim.
Please come back with findings/treatment/results !