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Hill Ascent It is usually best to tackle a hill climb that’s
any sort of challenge in low range. Although you may be able to just reach the top of a
hill climb in 1st high, it doesn't leave you with any lower gears if the need arises. By
using say 2nd or 3rd low range instead of 1st high, you have lower gears available if
needed. If you run out of gears on a hill climb, you may have to back down to the bottom of
the hill and start again. Most 5-speed gearboxes allow vehicles to travel up to 6Okm/h in
low range, so you don't have to be continually swapping between low and high range as you
travel between hills.
Diesel vehicles are generally better for hill
ascents and descents as they usually have better low rpm torque for climbing the hill and
higher engine compression for descending. However, in long sandy hill ascents, where
traction is low and a run-up is required, the greater power of gas engines can be an
advantage.
 Hill Descent
When descending hills, you should always be
in low range and have selected the gear required before descending. You should always
avoid braking on downhill sections as you run the risk of locking up your wheels, causing
a slide. Engine braking slows the vehicle without causing wheel lockup. However it is
better to use the brakes than allow the vehicle to 'run away' and pick up speed. Always
apply the brakes gently, rather than applying them abruptly and risking a wheel lockup.
Often hills get steeper the further you go down, so
its best to be in 1st low from the beginning rather than having to try and change gear
halfway down. When changing down a gear while descending, it is best to be feathering the
brakes as you depress the clutch, as otherwise the vehicle freewheels while the clutch is
depressed and picks up speed. It is far better to be in too low a gear and travel down
slowly rather than be in too high a gear and have a potentially dangerous situation arise.
Hill Stall
Recovery
A very common occurrence on hill climbs is the
stalling of the vehicle when the hill becomes too steep. When this occurs, you will be
left in gear with the engine switched on but stalled. To recover from this situation you
should perform a Hill Stall Recovery, rather than just fire up the engine. This is
accomplished by:
Switch the (stalled) engine off and place your foot firmly on the
brake.
Depress the clutch and select reverse gear in low range.
Take your foot off the clutch then slowly take your foot off the
brake. The vehicle is now in reverse gear with the stalled engine stopping it from rolling
down the hill.
After checking the track behind is clear, start the engine and keep
your feet off all pedals.
The starter motor will start to drive the vehicle backwards as the
engine begins to fire.
This will result in a smooth downhill progression
while starting the engine and ensuring you have been in gear at all times. If you
simply start the engine and then select reverse gear, it will result in a fast jerky
takeoff and being out of gear during some stage of the takeoff.
The Hill Stall Recovery does not apply to automatic
vehicles as they should never stall, just lose forward drive when the hill becomes too
steep for the gear its in. When this occurs, simply place your foot on the brake while
restarting the engine, select the appropriate gear and gently take your foot off the
brake.
A lesser used method after an uphill stall can be
done in situations where the terrain is not extremely steep and you wish to continue
forward up the hill but you do not wish to attempt to let the clutch out while trying due
to tire spin. This method only applies to manual transmissions and drive trains that
have very low forward gears. By leaving the vehicle in gear and starting the engine
without pressing the clutch in the vehicle will begin to move forward while the engine
fires. Once the engine fires you can begin forward movement. This method is
hard on the starter and electrical system and should not be attempted on very steep
terrain due to the possible overload on the electrical system and starter. Some
vehicles will not allow the starter to be engaged if the vehicle's clutch is not
depressed. In some cases this feature can be overridden by use of a clutch safety
cancel switch.
Vehicle Rollover
Hills should always be tackled straight up or down
and sideway slopes avoided like the plague. A vehicle has to be at an extreme angle for it
to roll head to tail, whereas a sideways roll can occur at much more modest angles. The
way your luggage is packed has a pronounced affect on the angle a vehicle will roll
sideways. You should avoid placing containers of extra fuel and water on the roof of your
vehicle, as this will significantly decrease the angle at which a rollover is possible.
This occurs because the extra weight on the top of a vehicle increases the 'center of
gravity'. Heavy gear should always be packed low inside the vehicle and as centered as
possible while only lightweight gear should be placed on roof racks.
The type of terrain will also affect
the sideways rollover angle. In sand, mud or other soft terrain the weight transfer to the
downhill wheels will cause them to sink, increasing the actual slope angle. So what may
appear an acceptable angle on firm terrain may result in a rollover on soft terrain.
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