Does Huck fear of going to hell?

No.

In chapter 31, Huck writes a letter to Miss Watson, telling her where the escaped slave Jim is. Then Huck thinks about his friendship with Jim and realizes that Jim will be sold down the river either way. He then destroys the letter. Logical consequences, rather that society's rules, drove Huck's actions. He decides that if going to hell results from following his instincts and disobeying hypocritical and cruel principles, it is better than going to heaven.