I'm building a function that takes a drupal rendered menu and removes the classes from it so that I can pass it to a jQuery function that'll build a menu from it.

The code i'm using for that is:- 

    <?php
         $tree = menu_tree_all_data("devel-frus");
         $menu = drupal_render(menu_tree_output($tree));
         $nocss = preg_replace('/class=".*?"/', '', $menu);
         echo($nocss);
    ?>
However `menu_tree_output()` seems to be only returning the first level of a six level menu when it should be returning the complete menu. 

I've tried `dsm()`'ing `$tree` to see if all of the menu items are being returned by `menu_tree_all_data()` and that's fine, however when I `dsm()` the output of the `menu_tree_output()` function only the root and first level are returned in the array. 

Am I doing something really obviously wrong here?