SIMILE HELP: Gripping the wheel tightly like [closed]
Try; Hold on for dear life; 'He grasped the wheel and hung on for dear life' or 'He held onto the wheel as if his life depended on it.'
'He held the wheel like a vice'
'He was gripping the wheel so tightly his knuckles shone white'
'He gripped the wheel so tightly, they would have to pry his fingers off with a crowbar'
Hope this helps.
How about:
Gripping the wheel as if you are on a roller coaster?
For a fauna alternative (mind you, it is somewhat contrived):
...like a boa constrictor chocking its prey.