I need special numbering for an article: (e.g. Part 1 should be numbered J4.1, the section below should be J4.1.1). I did this with:
\renewcommand{\thepart}{J4.\arabic{part}}
\setcounter{part}{0}
\renewcommand{\thesection}{J4.\arabic{part}.\arabic{section}}
\setcounter{section}{0}
The numbering works quite well, but now the position of the titles in the TOC is wrong. Also I get a warning message: Overfull \hbox (14.58316pt too wide) detected.

I tried using tocloft and setting the numwidth, but that didn't change anything.
Here is the complete code:
\documentclass[final]{article}
\usepackage[a4paper,left=25mm,right=25mm,top=2cm,bottom=2cm]{geometry}
\renewcommand{\thepart}{J4.\arabic{part}}
\setcounter{part}{0}
\renewcommand{\thesection}{J4.\arabic{part}.\arabic{section}}
\setcounter{section}{0}
\begin{document}
\tableofcontents
\part{Part 1}
\section{Section 1}
\section{Section 2}
\subsection{Sub 1 asasdasd}
\subsection{Sub 2 sdlkfjls}
\subsection{Sub 3 ksdfjhj}
\end{document}
Do you have any ideas? Thx!