You may need to ask your question again, this time supplying the model number and name. Since I have no idea if you will see this, let me supply for future readers a URL which has parts layouts, also some parts and I think tension assembly is one, for SOME Singer models, which will help only those who have those models. If your model is listed, click on button which says schematic for your model, and download it. If you print it, you will have a very useful listing of part numbers. My wife's 478 apparently just jumped a cog with the lower drive belt, and that parts listing was very helpful, and free.
Then, if your model is included, look elsewhere on URL for that part which may come with installation instructions.
http://www.sewusa.com/Sewing_Machine_Manuals/Singer_Repair_Manuals.htm
Bruce McGovern, April 2007
