Allison Automatic Transmission; Allison Transmission Cable Adjustments - Blue Bird Q - BUS Owner's Manual

MAINTENANCE
Service manuals supplied by converters and installers should be consulted for maintenance of NGV-specific
parts. Components such as the pressure regulator/reducer can be checked with a pressure gauge to deter-
mine if the unit is operating properly. Measurements with an EGA can indicate proper air/fuel mixtures and
ignition timing. NGV maintenance issues are briefly listed below.
CNG Cylinders - CNG cylinders must periodically be recertified to maintain compliance with DOT stan-
dards. The Compressed Gas Association has published several pamphlets with recommendations of stan-
dards for the inspection of compressed gas cylinders.
Oil Changes - Due to the clean burning characteristics of natural gas, collection of particulate matter in
engine oil does not occur as rapidly as with gasoline. However, even though visual inspection of the oil may
indicate that the oil is clean, oil compounds break down under engine heat. These chemical changes reduce
the lubricating ability of the oil and stress the engine system. Therefore, it is recommended that the oil should
be changed according to manufacturer recommendations, despite oil appearance. (NOTE: Considerably
more data is needed to determine the conditions that influence reports of NGV oil maintaining lubricating
properties longer than in gasoline engines.)
Spark Plugs - Spark plugs should be replaced as recommended by the vehicle manufacturer.
CAUTION: Do not use CNG pressure or vent lines to clamp, hang, connect or attach any items including
harnesses, hoses, power steering hose, refrigerant hoses or any other item.

ALLISON AUTOMATIC TRANSMISSION

AT 545 & MT 643
The Allison transmission provides four forward speeds and one reverse. Selective control is obtained
through the selector lever located on the right area of dash. The selector lever must be in "N" (neutral) to start
the engine. If the engine starts in any other position, the neutral start switch is malfunctioning. Use "D" for all
normal driving conditions. The vehicle will start in first gear and as you depress the accelerator, the transmis-
sion will upshift to second, third and fourth gear automatically. As the vehicle slows down, the transmission
will automatically downshift to the correct gear. Use (3&2) when the road load or traffic conditions make it
desirable to restrict the automatic shifting to a lower range. When the conditions improve, return the range
selector to the normal driving position. These positions also provide progressively greater engine braking
power (the lower the gear range, the greater the braking effect). Use (1) when pulling through mud and snow
or driving up steep grades. This position provides maximum engine braking power. Use R (reverse) for
backing the vehicle. The vehicle should be completely stopped before shifting from a forward gear to reverse.
Reverse gear provides the greatest tractive advantage.
CAUTION: In the lower ranges (1, 2 and 3) the transmission will upshift above the highest gear selected
when the recommended engine governed speed for that gear is exceeded.

ALLISON TRANSMISSION CABLE ADJUSTMENTS

To properly adjust the transmission shift cable, the following must be done.
1. Place the selector in neutral with the cable connected at the selector and disconnected at the transmis-
sion.
2. Find neutral on the transmission. (This is accomplished by rotating the manual range selector shaft
on the transmission all the way counterclockwise, then rotate it one click clockwise.)
3. Adjust the trunnion pin so that it slides easily in and out of the hole in the shift lever on the transmis-
sion. Check the neutral safety switch on the selector to be sure the engine will start only in neutral.
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