I have a 6/7 year old male lab. I’ve had him for 3 years and lately he has gotten very over protective of me. He is very aggressive outside but when he is inside he’s the biggest baby. He has been neutered.
Every time I take him outside, he growls, barks at anything and everything. My neighbors are very afraid of him. I don’t know what to do. This has been going on for about 6 months. I tell him no and I’ll smack his nose but he doesn’t stop until I take him back inside.
I’m afraid to take him for walks because I’m afraid he might bite someone. He has never bitten anyone since I’ve had him. I can control him but I don’t want to take the chance. Once he knows people he is a very friendly typical lab. When someone comes into my house Jack is well behaved. He doesn’t bark at them or growl. But if that same person first encounters Jack outside he’s ready to attack.
He doesn’t like other dogs but that doesn’t make sense because until a year ago he has always lived with another dog. When I first got him I had a beagle and then he lived with another lab for 2 years. He has always been the Alpha dog.
I don’t know much about him before I got him. I believe he was abused. The first 8 months that I had him he was impossible to discipline because he would cower and have an accident and it just broke my heart. I don’t know if he ran away from home or he was dumped.
I don’t know what to do.

After 3 years in your care and at the age of 6-7 years, I would expect the dog's personality to be stable. As in most cases of a new problem behavior, start with a vet exam explaining the problem to the vet. Also, try to think of what other changes may be going on to disrupt his life,

If the vet doesn't turn up anything, I would try obedience training and exerting yourself as top dog. If you are top dog, it is your responsibility to deal with menacing strangers. 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 Raising Your Dog with the Monks of New Skete For more on being top dog, see Establishing and Keeping Alpha Position

Yes there has been some shifts in Jack's environment. We just moved to another state and for the first time since I've had Jack it's just me and him. So part of it might be the fact that there is not a male family member. I guess I need to work on being the leader of the pack. I can't figure out why when I lived with my dad Jack accepted my dad as the leader without any problems.

It could be he feels he must protect you now that your dad isn't there.

How do you know when you have become the alpha dog? I posted several weeks ago about my 6 yrs old male lab who is/was very aggressive. I have been retraining my lab and I am seeing some improvement. He fought me really hard for about 2 weeks but now he does do what I ask i.e. (I get to go outside first) he has to sit until I tell him to come. However he still wants to attack everything that moves outside? Any more suggestions?

I had a dog that new every command known to man and was fine as long as I was there . But as soon as one thing happened out of the ordinary. His hackles were up and he was ready to attack. And This gets very hard to live with, it is a constant worry. He was fine with other dogs but anything else 4 legs or 2 legs he was on watch and ready. I have no answers for you but I know what you are going threw.

I merged your questions making it easier to see what you were advised and the original problem.

Reshaping a 6-7 year old dog will not happen over night. It sounds like you are making good progress. You will know he has accepted you as top dog when he doesn't fight to go through the door, moves out of the way when he sees you coming, etc. Try to control your emotions when he is barking and growling. Tell him leave it or enough. Then down stay him. Keep up a happy patter. It is really better to start having him focus on you before he reacts to the person dog. Start while they are still a little ways off. Do what you can to avoid showing stress. It is very hard to hide emotions from a dog. Any tension he senses on you, he will interpret as the fault of the person or other dog, not his barking at it. Once he quiets down, release him and let him greet the other. If he starts barking or growling, down stay him again.

I once saw a great demonstration of this. As we were going in the door to the hotel, her German Shepherd growled at some teenagers coming out. She corrected the dog and then put it in a down stay and made the kids pet it. They were uneasy about the dog, but not about to cross her.

A big advantage of an obedience class is the other dogs. You can't teach your dog to behave well around other dogs without them. A good instructor will see things you won't see and point them out to you.

My friend is a 4-H dog leader. I will be taking my Holly to her meeting tonight. It is not that I need the training, but it gives her other dogs to practice ignoring. She recruits kids to show the dog guide puppies. The kids do a nice job sharpening up the dogs obedience and it prepares the dogs to work with their new trainers when they go off to school. So a class is a help to anybody when it comes to how the dog behaves around other dogs.

Labman is correct. When you are outside and the dog is on a leash you must anticipate (but not panic) about what your dogs reaction to a approaching person will be. You must be ready to immediately jerk the leash with a command of "LEAVE IT" or "ENOUGH". You have to be able to anticipate this and act within a second or less of your dog reacting. If you are the "Alpha" your dog will listen. But it is a good idea to go to a group obedience class and work with others. Try to find a UKC or AKC good citizen class as this will teach your dog how to behave around other people and other dogs.