Aggression or excited to play?

Hey folks,
Quite recently, i've been taking my dog, Sable (one year old GSD )to attend private obedience classes. The main reason why my boyfriend and I decided to take Sable for private classes is so that we can learn to lay down the foundations of her basic obedience before introducing her to an environment with other dogs and then gradually schutzhund. At the moment, she is the only dog in our household. But for christmas, we will spending time with family up north, who has 2 other dogs (GSD & Collie Mix, GSD & Husky mix). Previously, Sable has spent some time living with these 2 dogs for 4-6 months. Watching her behaviour, she doesn't seem aggressive, although she really likes to BITE, not nip, but bite hard on the GSD & Collie mix (usually the neck, ears or back legs), which very often ends up in a fight because sable is relentless on biting. And the other dog, who usually doesn't fight or play back, becomes mad for Sable's stubborness.
Aside from these 2 family dogs, I have noticed that Sable has a tendency to be "aggressive" when she sees other dogs. I say "aggressive" because i am not sure if it is indeed aggression. What she does is barks (in a lower deeper tone), and lunges. If the dog barks back, on rare occassion her fur stands or as my boyfriend calls it... a butt-hawk (as opposed to a mohawk, har har.. lame joke, we know :D ) - So far, I've only seen that happen twice. She whines excessively and so far hasn't growled, or shown her teeth. Her posture is one that leans forward as opposed to shrinking away from the other dog and her tail doesn't wag excitedly.
We have taken her to a dog park once, and played fetch with her on the field. When a dog came running from the corner, Sable decided to gun it and chased the dog... once caught up to the dog, she jumped and attempted to bite him. I'm not sure if it was a playful bite (like the ones she usually would do to the family dogs) but i can assure you that the other dog did not appreciate it. Ever since then we do not let her off-leash.
So far whenever Sable sees other dogs, this has always been her reaction - wild and out of control. Luckily, with the training, the level of wildness has toned down a bit... Apart from that, things have been going very well. She learns her commands very quickly and listens well.
Can i have any advice? Does Sable have dog aggression or is she just too excited to play when she sees other dogs?

Sounds like baaaaaad manners. Your dog is pulling bad dominant moves on these other doggies, and I'm guessing he's generally younger than them. IMO, you really have to be in a position to correct this because if you leave it for the other dog to correct, chances are it'll break out into a fight every time. Your dog just hasn't been taught that he isn't top dog and he just won't stand down because of that.

I think it starts with you. Once he is very clear that you are the leader, then you can move on to other dogs and being in a better position to correct the behaviors with the other dogs.:shrug:

That is aggressive behaviour. What kind of socializing have you done with her.

I'd put schutzhund on the back back burner. Wanting to train for that should be the least of your concerns, your dog has far too many issues to need correcting first.

yeah, being fully aware of how sable is with other dogs. Schutzhund is not going to be happening any time soon or in the near future - up until we've resolved the dog aggression issue.

As for bad behaviour, we try to stop her from such aggressive dominant moves. Unfortunately, she listens when we're in the room... so as soon as they are left out to play, sable turns around and does it again up until we come back. STUBBORN, i say! After that she acts like a perfect angel. As a result, i've decided that she cannot be left alone with the other house dogs unsupervised.

Apart from seeing the 2 family dogs once in every a couple of months, she hasn't had other opportunities to socialise - even before living with me, those dogs were the only interaction she's had. Now that she's living with me in toronto, we're gradually exposing her to environment with dogs.

I want to start positive reinforcement with her when there are dogs around, however finding someone with another dog who is willing to help me train her is proving to be very challenging.

Any ideas on how i can tackle this problem?

You may consider seeking out a trainer who uses his/her OWN dog to help. when I took training classes, our trainer frequently brought in his older BMD to assist. this dog was perfectly trained, older, calm, and very stable. He was a fabulous "assistant" - and really helped all the dogs overcome obstacles. perhaps you can find something similar in your area.

just a suggestion.