After replacing just about everything in the front end of my 190e I'm having a fairly difficult time tracking down a wander at highway speed. One thing I've noticed is that my steering wheel doesn't really seem to return to center very well if at all. I've heard this can be caused by overtightening the steering box and when I went to try and loosen it I found the locknut seized. If I turn the wheel 180 degrees while stopped and start driving it'll correct to about 50-60 degrees of center. I have just about 1 inch of play in the wheel but it is fairly heavy to turn as well.

Is there anyway to determine the gear is bad before I drop $300 on a new one?

I believe my wander is due to the steering wheel not wanting to center and following any imperfections in the road. Alignment was done and caster is 10.2 both sides. I've replaced the following: LCAs w/ ball joints, entire tie rods, center link, idler arm bushings, steering damper, springs and struts are also new. Am I missing anything else?