I have two 20 month old Sisters who are fantastically well behaved in the house very loving to each other and sleep together all cuddled up.

However take them both out together and within minutes they are wanting to rip each other throats out literally!!

Dot is the bigger of the wo and I would say the cause of most of the fights, she has a tendency to cling onto her sisters tail constantly when she is out but will go off and do her own thing as well, but the aggression simply isn't on.

They have got to the point of both being on hind legs and a total lead lock and being very mean to each other I am scared one of them is going to end up seriously hurt.

I know the simple thing would be to walk them separately but once they have the fight they get on OK again and I hate to separate them as they are muiserable when I do.

I s this simply a dominace thing to do with their ages? They are both neuteured, wouldn't have it any other way anad this aside they get on great and are generally content

You did not state what breed they are.

They get along all right, like Cain and Abel. You could try this, start by going out with them both, stay right by the house. Just as soon as you see this behaviour beginning on anyone's part, immediately reprimand the dog like I would say, "quit picking on your sister" in a commanding no fooling around tone. My dad would use that line from "It's A Wonderful Life" settle yourselves! Do you think I'm talking into my hat? If you don't get the desired response then you tell both dogs that is IT, we are going right back inside now. Walk and fun is over. Then try again short time later. Like when dad used to say, that's IT, I'm turning this car around right now and going back home, we are not going for ice cream. If you get cooperation from one dog and not the other then good dog gets to stay and misbehaves dog has to immediately go in where she can look out the window and see good dog having a good time. It won't kill her. Like giving a toddler timeout.