Auto gear selection for towing.

[Rab]

I have towed around 3T fairly regularly and have been impressed with the programming of the gearbox when fully laden (mostly livestock).
With live animals a smooth transition up and down the speed range is essential and in my opinion, when using auto, it is very well judged.
It also negates the need to use the manual function on steeper downhill sections as it automatically selects a lower gear to increase the engine braking effect.
I used to have the off-road screen up when towing to keep an eye on all the temperatures as there are some long steep grades to contend with on the way to the markets but found everything remained quite stable.
This is the diesel variant, I had a petrol on loan for three days and thought there was a hole in the tank.

 

[Tinerfeño]

... on steeper downhill sections as it automatically selects a lower gear to increase the engine braking effect.

Never seen this happen

 

[Clark Kent]

Never seen this happen

I get this also. Coasting downhill with light braking the trans will often downshift to increase engine braking. It's very cool.
Diesel with 8HP76 trans.

 

[Eric]

Never seen this happen

It does if you brake going down hill, (diesel) that's why on tarmac it is easier to stay in auto.

 

[Tinerfeño]

Mine's a petrol.
It may be also for increased charging.
I need to test this.

 

[Dokatd]

If you find your truck dropping out of 8th a fair bit to catch up, then I would go manual 7th. Otherwise let it do its thing.

I ran into this mostly with my P38 Range Rover while towing my crawler. The trans would overheat from downshifting from OD constantly. Dropping it down a gear fixed the issue. This was on regular yearly trips over 2400mi round trip.