Tiffin Motorhomes ALLEGRO BREEZE, Owner'S Manual

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A L L I S O N T R A N S M I S S I O N O P E R A T I O N
2-2
Operation
The Allegro Red 340 with the Powerglide Chassis is equipped with an Allison 2500MH transmission.
The display screen on the shift control pad will indicate the highest selected gear for the transmission. When
mountainous or up-and-down terrain conditions are encountered, you should manually select a lower gear ,
preferably lower than 5 th gear. This can be done at any road speed by pressing the down arrow repeatedly until
the desired gear is indicated in the window of the shifter pad. When your road speed decreases to a safe point,
the transmission will downshift at a higher RPM than normal. This will decrease the use of overdrive while
pulling hills, which can result in excessive heat build-up in the transmission, and keeps the engine operating at
peak horse power and performance.
When ascending a grade, maintain engine speed to within 400-500 RPM of governed engine speed. Governed
speed will be 2800 RPM on the Cummins ISB engine model. Road speed may decrease, but the engine will be
at its peak in the power curve.
It is especially pertinent to monitor your water temperature gauge when climbing steep grades. Keep in mind
that it is not uncommon for the temperature to increase, especially in hot weather. If the gauge reaches 225°F
or if the temperature warning light on the gauge panel should come on, reduce your road speed, shift to the
next lower gear and keep your tachometer within 500 RPM of engine governed speed. In many cases this will
stabilize the water temperature. If the temperature gauge continues to rise, or if the stop engine light comes on,
pull to the side of the road and shift the transmission into neutral. Bring the engine RPM to 1,700—2,000
RPM until the temperature drops down into the normal range. This should occur in a relatively short period of
time. If the temperature gauge does not begin to drop, stays in the red zone, or continues to rise, shut down the
engine and allow it to cool. After the engine is allowed to cool check the fluid level in the reservoir and add
coolant if needed.
A good “ rule of thumb ” for descending grades is to never use a higher gear than was used to climb the same
or similar grade. Try to keep the engine within 500 RPM of governed speed. This will give the best engine
braking and reduce the need to use the service brakes. Select a gear that will keep you at a safe speed with
minimal brake application. Never ride your brakes when descending a grade since excessive brake heat will
build up and your brakes could fade, leaving you with little or no braking power.
Your vehicle is equipped with an engine brake. The engine brake will assist in slowing your vehicle on a
downhill grade. With the engine brake switch in the on position, release the accelerator and depress the service
brake to activate the engine brake. When the engine brake is activated the transmission will pre-select a lower
gear to aid in braking. This is indicated by a “2” in the left hand pane of the transmission shift selector. The
transmission will begin to down-shift as soon as the road and engine speed will safely allow. This will produce a
slowing effect and will remain engaged until ether the exhaust brake switch is turned off, the accelerator is
pressed, or the engine speed drops to 800 RPM. If your initial speed is high, you may have to step on the brake
to slow the vehicle before the transmission will down-shift from 6
th
gear to 5
th
gear. This is normal.
Always select ( N ) neutral on the transmission shift pad prior to turning off the vehicle engine.