GMC 1994 Yukon Owner's Manual page 202

Making Turns
When you're turning with a trailer, make wider turns than normal. Do this
so your trailer won't strike soft shoulders, curbs, road signs, trees, or other
objects. Avoid jerky or sudden maneuvers. Signal well in advance.
Turn Signals When Towing a Trailer
When you tow a trailer, your vehicle has to have a different turn signal
flasher and extra wiring. The green arrows on your instrument panel will
flash whenever you signal a turn or lane change. Properly hooked up, the
trailer lights will also flash, telling other drivers you're about to turn,
change lanes or stop.
When towing a trailer, the green arrows on your instrument panel will flash
for turns even if the bulbs on the trailer are burned out. Thus, you may think
drivers behind you are seeing your signal when they are not. It's important
to check occasionally to be sure the trailer bulbs are still working.
Driving On Grades
Reduce speed and shift to a lower gear before you start down a long or
steep downgrade. If you don't shift down, you might have to use your
brakes so much that they would get hot and no longer work well.
On a long uphill grade, shift down and reduce your speed
to
around 45 mph
(70 km/h) to reduce the possibility of engine and transmission overheating.
When towing at high altitude with steep uphill grades, you need to consider
the following information. The lower atmospheric pressure at high altitude
allows your vehicles engine coolant to boil at a lower temperature than at
normal altitudes.
If you immediately turn your engine off after towing at high altitude with
steep uphill grades, your vehicle may show signs similar to engine
overheating. To avoid this, let your vehicle operate in a parked position with
the transmission in "N" (Neutral) for a few minutes before you turn off the
engine. If you do get the overheat warning, see "Engine Overheating" in
the Index.
If you have an automatic transmission, you should use "D" (or, as you need
to, a lower gear) when towing a trailer. Operating your vehicle in "D" when
towing a trailer will minimize heat buildup and extend the life of your
transmission.
If you have a manual transmission and you are towing a trailer, it's better
not to use fifth gear. Just drive in fourth gear (or, as you need toy a lower
gear).
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