jack russell behaviour

Question
I have 2 Jack Russell pups brother and sister aged 9 months, both are lovely dogs in the house, but the dog who has been castrated chases trains cars skate boards etc etc , and chases other dogs whilst out walking , he runs at them barking and growling and has been known to nip them, is there anything i can do or use to sort this problem out ,it seems to have started after he was castrated as he was a sweetie before, but it could also be because he is getting a bit older. I am at my wits end and do not want to have to keep him on the lead and away from other dogs.  

Answer
Hello Sarah,

This is definitely a problem yes?! There is no quick and easy solution but it is not hopeless! Unfortunately you have to start from scratch and retrain him.  Trust me his behavior has nothing to do with being neutered. I would like to kindly suggest that you look into the Cesar Milan method of dog training. Here in the US he is a very well known and established dog trainer with excellent results.
He sells videos and books right on his website that will help you immensely! If I had the space I could write down the method for you but I'm afraid it wouldn't fit. He has methods that you can do yourself at home, you don't need to be hiring anyone, but the videos are a great investment and not very expensive.   
Here are the links to his various sites, I KNOW you will find some help here. I wish you the very best of luck!  

http://channel.nationalgeographic.com/channel/dogwhisperer/

http://www.dogpsychologycenter.com/