animal aggresion

Question
I have had shepherds for over 30 years, I love the breed.  I curantly have a 4.5
year old neutered male weighing 130 pounds whom is one of the most
intelligent dogs I have ever had.  He is very protective of his domain,
(intensely
so but not vicious).  When we are getting ready to take him somewhere or
when we are riding to our destination his excitement so over whelms him that
he will, (for lack of a better description), simply scream.  Once we are walking
he does well, is easy to direct and redirect until another dog enters the area.  
Doesn't mater the size, breed, sex.  Louie becomes ballistic and looses all
ability to listen, pay attention or be redirected.  Without both harness and
choker on him and my strong husband on the lead we would not be able to
keep him from an ugly encounter.  When we see another dog coming we back
Louie out of the area and then tell him to sit and stay, which he does until he
sees the dog, then the ballistic screaming behavior starts.  The other
shepherd that we have just sits there, all the other shepherds I have had will
simply do what is asked.  Louie just looses it.  We have never experienced this
with any of our other 9 shepherds and are at a lose as what to do.

Answer
I think it is quite obvious he is not accepting you as leader.  Even if he has had obedience training and obeys standard commands, you don't have the right relationship with him.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

The problem may come from poor early socialization, perhaps even before you got him.  Undoing mistakes in a dogs first 12 weeks is always difficult and more so having had 4 1/2 years to mature and establish a behavior problem.  What I suggested above may not be enough.  As hard as they are to find, you may need a good private trainer.  I am afraid too many of those practicing need more practice.  Look for one with some training, not 25 years of repeating the same mistakes.