Newbie Towing Question

I tow with a Mercedes ML320- It's a big 6 banger. When in the mountains, I watch my temperature gauge pretty closely. I don't push it and keep my flashers on as soon as I drop below 50 or so. Usually I'm right in there with really loaded semis. So far I haven't had any issues but I don't break any land speed barriers either. Fortunately, most of these types of grades are pretty short.

Phil

I would check the highlander manual, most of the time it is recommended to turn off the OD when towing. Usually a switch or button ( on auto trans) . This makes for better trans cooling and less strain on the trans. It will hurt your mileage but save your transmission. Once back on fairly level ground, you can turn OD back on.