In a document at my workplace, \autoref is redefined in the following way:
\renewcommand{\autoref}[1]{\cref{#1}}
I suppose this is important because it probably means that I cannot just overwrite \equationautorefname.
For equations, this results in something like "Equation (5.1)". The parenthis are fine when they are shown next to the equation, but in the text we want them to be displayed without the parenthesis.
How can I achieve this?

equation \ref{eq:5.1}, as you say, you don't want the parens, but that's a subjective choice. gonzalo's answer appears to do the job compactly. – barbara beeton Sep 03 '13 at 15:08