As far as I understand, both "attempt" and "try" describe active measures towards achieving a goal. Words like "aim", "seek" are listed as synonyms, but seem not to indicate active measures.
What is the difference between:
I am trying to fix the car
I tried to fix the car
I am attempting to fix the car (sounds unnatural)
I attempted to fix the car
Personally, I think that "attempt" indicates one shot quick look (attempted, but was too much effort) and "try" indicates prolonged efforts (done everything I could)