I recently upgraded to Autocad 2015 Mechanical and I cant seem to go back to classic view
Dean is correct, the "classic" workspace has been removed in the 2015 release of AutoCAD. This includes the "mechanical classic" workspace for AutoCAD Mechanical. However, with use of the Customize User Interface (CUI) you are able to create a customized workspace. The following link will provide additional information on how to work with the CUI.
How to work with the CUIx to Customize AutoCAD (AU 2013 Class)
Should you have any further questions on how to customize a mechanical workspace, it would be best suited to post your inquiry to the mechanical forums (see Dean's post above)
Regards,
In addition to my previous response, you may also want to review the following links as well.
The AutoCAD classis workspace is not available in AutoCAD 2015
How to migrate settings from a previous version of AutoCAD Mechanical
Please check "Accept as Solution" if this resolves your inquiry.
Regards,