Those fittings get rusted and real tight. You can use a standard non-metric 5/8 inch line wrench on the tube nuts and get a very good fit. Have to work it some to get it on but you can really put some torque on it without rounding off the hex.

 

Yup! Same deal on the transmission cooler lines.. A 1/2" Crows foot on an extension is the only way to do it!! Try to use a 13mm like its "supposed" to be, and you'll round it quick..