I downloaded the Owner's Manual for a 2015 Dodge Grand Caravan. See page 545-546 under towing:
Towing Tips
Before setting out on a trip, practice turning, stopping,
and backing up the trailer in an area located away from
heavy traffic.
Automatic Transmission
The DRIVE gear can be selected when towing. However,
if frequent shifting occurs while in DRIVE, use the
Electronic Range Select (ERS) shift control to select a
lower gear range.
NOTE: Using a lower gear range while operating the
vehicle under heavy loading conditions will improve
performance and extend transmission life by reducing
excessive shifting and heat build up. This action will also
provide better engine braking.
If you REGULARLY tow a trailer for more than 45
minutes of continuous operation, then change the transmission
fluid and filter as specified for “police, taxi, fleet,
or frequent trailer towing.” Refer to the “Maintenance
Schedule” for the proper maintenance intervals.
Electronic Speed Control — If Equipped
• Do not use in hilly terrain or with heavy loads.
• When using the speed control, if you experience speed
drops greater than 10 mph (16 km/h), disengage until
you can get back to cruising speed.
• Use speed control in flat terrain and with light loads to
maximize fuel efficiency.
Cooling System
To reduce potential for engine and transmission overheating,
take the following actions:
City Driving
When stopped for short periods, shift the transmission
into NEUTRAL and increase engine idle speed.
Highway Driving
Reduce speed.
Air Conditioning
Turn off temporarily.
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I suspect your son has a User's Guide which only has the basic information.
See page 462 for driving in heavy load conditions, hilly terrain, strong head winds or towing heavy trailers.
When frequent transmission shifting occurs (such as
when operating the vehicle under heavy loading conditions,
in hilly terrain, traveling into strong head winds, or
while towing heavy trailers),
use the Electronic Range
Select (ERS) shift control (refer to Electronic Range Select
(ERS) Operation in this section for further information)
to select a lower gear range. Under these conditions,
using a lower gear range will improve performance and
extend transmission life by reducing excessive shifting
and heat buildup.
P. 464
Electronic Range Select (ERS) Operation
The Electronic Range Select (ERS) shift control allows the
driver to limit the highest available gear when the
transmission is in DRIVE. For example, if you shift the
transmission into 4 (fourth gear), the transmission will
not shift above fourth gear (except to prevent engine
overspeed), but will shift through the lower gears normally.
You can switch between DRIVE and ERS mode at any
vehicle speed. When the shift lever is in the DRIVE
position, the transmission will operate automatically,
shifting between all available gears. Tapping the shift
lever to the left (-) will activate ERS mode, display the
current gear in the instrument cluster, and maintain that
gear as the top available gear. Once in ERS mode, tapping
the shift lever to the left (-) or right (+) will change the top
available gear.
To exit ERS mode, simply hold the shift lever to the right
(+) until “D” is once again displayed in the instrument
