School me on trans basics

after reading around, I think I'm going to put my sender in the oil pin. Reason is not all the fluid makes its way through the cooler. Some empties directly back into the pan. So you could have different temps in the to cooler line, from cooler line, and in the pan. I'm thinking I'll go off the temp of fluid in the pan the trans will be drawing in..now I have zero actual experience with this, so I'm open to any and all suggestions..