Hi, again.
Very sorry I never got back to you -- perhaps this will explain:
http://www.brickboard.com/OPINIONS/?id=1202847
I didn't know that you responded until now (and I believe that KlausC was in the same predicament that I was).

Anyway, I'm glad you're going to get the auxiliary cooler -- it will go a long way to making your transmission last, because it's life (and the life of it's fluid) is a function of the maximum temperatures it encounters.

And yes, the cars of the 1960's and early '70's could pull a lot, even though even they usually needed some helper springs or air shocks to cope with tongue weight -- they were just behemouths with stout frames (our Volvos really don't have a frame for torsional rigidity), big rear axles, massive weight, and big engines with transmissions to match -- even my old '57 and '60's Chevies had a mere six that was 235 ci, almost twice the displacement of our 4 and 5-cylinder Volvos. They just "muscled" the trailer, like the proverbial "600 lb gorilla".

Best regards,