Transmission Cooler

[Guest]

I have a 1999 EB 4x4 with no tow package (no trailer hitch anyway). I'm going to install a hitch and start towing a boat this spring, so I called a transmssion shop to see if they would install a transmission cooler. They said that I already have one inside the radiator and that the only thing I could add would be an external mounted cooler. Is this true? I was under the assumption that transmssion coolers were part of the tow package and that if I didn't have the tow package then no cooler. If I have an internal trans cooler, does it make sense to install an external cooler too? Any insight appreciated.

Thanks