We have a four year old Blue heeler. Is the BEST dog anyone could ask for. Obedience is great- Only problem we can't seem to correct is when he is in the car. He has separation anxiety(He was also a rescue dog which I think may be the cause). When we leave him in the car/truck to grab a pop-or even just to put gas in the car he carries (barking and howling) on the entire time. I don’t want to put a shock collar on him- we need another way. Also, when he is in the car he barks and cries when we start to slow down jumps from the back seat to the front (gets way too excited that we are about to stop and play) its ear-piercing and I don’t know how to correct a behavior that is from excitement. We are about to get another heeler. I think that he will be a great example to a younger puppy--but I don't want him teaching this bad habit.

You may want to consider taking some time to try and desensitize him to being in the car. Try just working with him at home in the driveway with a long lead. Practice getting him to sit and stay in the vehicle while the door is still open increasing the distance in which you back away from the vehicle. Any time he calmly sits and waits give him whatever treat he loves best and praise him lavishly. Once you can get out a good distance from the car while he remains calm then you can start trying to close the door for only a few seconds at first and with you right next to the vehicle. Every time he sits quietly and calmly reward him and once again slowly increase the time and distance from the vehicle. I'm not promising you this will work and it may take a lot of patience but the key to key to training him is positive reinforcement here. I believe that if being in the vehicle causes the level of stress you say it does already then something painful like a shock collar would only be severely detrimental to trying to help solve the anxiety problem and you are very right to not even consider this option.

Silverfoxkit is dead on.

You need to get her used to just being in the car while it is still on your property.

Use whatever she responds to best, treats, toys etc. and lure her into the car.
She doesn't have to stay in there long, just a hop in and out is fine the first time.
Gradually increase the amount of time she is there for until you have her comfortably getting into the car.

Then you can move onto closing the doors.
Do the same as you did before, just short amounts of time to start with, then build it up.

Once you are good with that just do short trips.
Even backing your car to the end of the drive, then going forward again.
If she doesn't cry, give her lots of praise and let her out of the car.
Increase the length of the drives and by the end you should have a pup that loves car trips :)

We have a four year old Blue heeler that is very well trained but barks in the car- I've posted a this question before but maybe need to be more specific. I've come to two reasons he cries and carries on- which is why we need so much help with this. I don't think it has anything to do with the car because he is more than happy to get in the car.
One) he has severe separation anxiety- wants to be with us all the time. I think the fear of being left in the car by himself causes him to throw a barking fit even if we haven't stopped and gotten out of the car yet.He knows we will stop soon and is saying don't forget me. He will even carry on if just one of us gets of the car.
Two) He likes to sit next to one of us and likes to see where he is going-that is why he isn't too bad in our truck (has a bench seat for him to relax and look out the window).

We had a trainers advice to tug on his leash and tell him no barking. This was working but he is now just sitting back far enough to not feel the tug. This is very frustrating because this shows us that he KNOWS he is not aloud to bark like this.
We love this breed of dog and have discussed getting another dog for quite a few months now as another companion for us and Scooter. Do you think that another companion will help with separation anxiety? Having another dog with him won't make him panic so much? We love to take him everywhere and we always make several trips during the week fishing and hiking-this barking is very frustrating and sometimes makes us rethink taking him on longer car-rides.
We rescued him when he was a little over a year- I know he had been bounced in a few different homes- I am fairly confident this is why we have this problem with him.

I have had two dogs with separation anxiety and getting another dog did help.

Have you tried taking him to a park and having fun with him sometimes when you go on rides?
If he sees that every trip isn't about your leaving him in the car he might do better.
That way he will learn not to 'expect' that you will be getting out and leaving him alone every time.
Do you leave him in the car alone for long periods?
Maybe giving him a doggie biscuit or treat when he rides without barking might be helpful too.

Well we don't take him if he isn't able to get out. He goes on a couple trips a week fishing or hiking. I take him every Thursday to doggie day at the park.

Maybe he is just so excited that you are taking him and he thinks barking is his way of telling you that.
I don't know what you can do to make him stop.

I was saying that in my first question I posted about him. I think he's just so excited to go explore he goes on a barking fit-- sometimes its to pout he has to sit in the car for a few minutes and other times its because he's so excited--how do I correct excitement? Even in the house, I will ask him to sit or do a command to calm himself down and stop jumping around--and I will praise him and tell him what a great job he's doing-he gets so excited that I told him he was a god boy-he starts jumping forgetting I told him to do a command to calm down. We are really at confusion on how to deal with this

Just like a kid :D
They carry on about going but love going.
I still get the Maw when we going to get there and they are grown now.

I am sure he loves being your baby.

Does he do it as soon as you get in the car?
Or only when he knows where he is going?

Does he like toys?
Something like a kong filled with a his favourite treat could be a good distraction in the car.

This may not be received very well but something like a rolled up newspaper could work if he is in the back.
If he is barking just give him a tap on the shoulder with it as a correction followed by a "no barking"

Have you thought about something like a citronella collar?
They are a collar that goes around the dogs neack with a box at the front.
When the dog barks the box sprays citronella upwards towards their nose.
They can't stand the smell and usually catch on that barking means a spray with nasty liquid within a few days.

What will they come up with next?
When I was a kid I always thought there just had to be some simple trick to make a dog stop barking.

Yeah pretty much.
It's a lot kinder than the shock collars though, they are as a last resort only, same with debarking.

My mum just bought one, she is going to start using it soon.
Her Great Dane is an absolute mouth.
We have tried everything to get him to stop barking with no luck, it's not barking at people/cars/things, it is just random barking at nothing, hopefully this will help.

With mine I usually threaten them with the newspaper, Prada has never been tapped/hit by it but Brody has. They both stop as soon as I pick it up and just growl instead of barking.

That sort of punishment is very personal though, a lot of people don't like to do it.
Tugging at the leash like the OP said is another similar way of disciplining them that doesn't involve actual "hitting"
I have gotten a few reddies for that comment before so I can probably expect a few again now.

I could never debark a dog no matter how much they barked. I would send it to go live with someone in the country before I could do that.

I only agree with it when it's a case of the dog causing a lot of trouble (eg: with neighbours)
And the dog cannot be rehomed (too old, bad temperament etc )

If someone just does it without even trying to train the dog then no, I definitely do not agree.