Towing button on shifter

As above we use it going downhill mostly, but when going up hill if the trans shifts more than once I engage it also and the "hunting" goes away.

What it effectively does on upshifts is extend the shifting range, i.e. shifts at higher rpm, and on the way down hill will hold a lower gear without being manually shifted. The trans will downshift on it's own if you push the brakes and scrub off some speed, somewhere between 5-10 mph reduction triggers it seems.

As Effy stated. Changes the shift pattern for the transmission. Makes it a bit more aggressive with shift points when slowing down and accelerating.

Use it anytime you want, won't hurt the engine or transmission. The computers will protect both. Play around with it to get an idea how it fits with your driving patterns.

I use it quite a bit and not just for towing. The F53 V10 tow feature acts as an engine brake as well as better torque for pulling loads and grades. When going down descents, press the button and when you hit the brakes, the transmission will drop to a lower gear, hit it again and will drop further etc. I have gone down 6% grades using it and never had to actually use my brakes to slow me down. I also use it in traffic as the lower gear helps slow you down, again using the engine to brake more than the brakes. The button simply changes the shifting for better pulling and braking. I wouldn’t use it on the highway.