Why won't "sudo cd" work?
Instead try using sudo -s to start a root shell and then simply cd into the directory.
When you're done as root, press CtrlD or type exit.
As Arjan hints at in his comment below, it is important to note that as root, one can easily do damage to essential system components. Use with care!
cd is a shell builtin. sudo only works with executables. You could do sudo sh -c 'cd dirname' but as soon as the shell exits, you're returned to the directory you started from. If you say what it is you're trying to accomplish then I can help you find a way to do that.
You can simply su to become root and then cd all you want... I know an answer has already been accepted, but if one is not on the sudoers list then this is the only option.