Using The AllisonWorld Transmiss ion Shif t Se lec tor

The touch pad

commonly found in

motorhomes equipped

with this transmission is

more than just a gear

selector. It serves as a

communication link

between the

transmission and the

operator.

By CAROL F. MAXWELL &E.S. GURDJIAN, F76350

llison introduced its WorldTransmission to themotorhome marketplace

several years ago. The MD versionused in motorhomes was followedby the HD version, which is used inconjunction with engines havinghorsepower ratings in excess of 300,primarily heavier bus conversions.Although minor programmingdifferences exist to accommodatethe extra work load encountered bythe HD version both versions of the

A

World Transmission are six-speed units with electroniccontrols that function in asimilar fashion. Thissophisticated, electronicallycontrolled transmissionprovides more functions andfeatures than automatictransmissions of the past.

Transmission functionsand features. The AllisonWorld Transmission can adaptits shift schedule toaccommodate driving habits.It “learns” to shift accordingto the acceleration pattern andwill adapt to a different driverwithin a short period of time.It is programmed with analternate shift schedule, or(secondary mode) function,which will be discussed laterin the article. It canautomatically downshift asmany as two gears, withinrpm limits, during enginebraking to provide maximumbrake horsepower. In addition,it will automatically upshift orprevent downshifts toeliminate an engine over-revcondition. Original equipmentmanufacturer (OEM)specified downshift schedules canbe made available for use withexhaust brakes. This causes thetransmission to downshift to a lowergear to enhance engine brakeperformance, provided that this doesnot exceed maximum engine rpm.

The World Transmission has ashallow oil pan option, whichincreases ground clearance in pusherapplications. It has an oil sensoroption to detect transmission oillevel, a feature that is now suppliedautomatically with the shallow oilpan option.

The transmission can detectmalfunctions and protects itself byilluminating a dash-mounted “DONOT SHIFT” warning light. It willthen shift hydraulically to a defaultgear in “Convertor Mode” andrelease the lock-up clutch. Thisprotects the transmission and allowstravel with a restricted gear range toobtain service.

As expected, a sophisticatedtransmission needs an equallysophisticated shift selector. Allisonsupplies either a touch pad or lever-type shift selector. Mostmotorhomes with the MD-3060transmission have the touch pads sowe will focus on that type.

Shift Selector Functions:• To select gears.• To indicate the status of the

transmission.• To select a secondary mode of

operation.• To electronically check oil level

(if so equipped).• To clear a temporary “DO NOT

SHIFT” light.• To indicate the fault causing the

“DO NOT SHIFT” status.• To record, store, and play back

the last five diagnostic codes.The pad has six push buttons,

labeled "R," "N," "D," "↑" "↓" and"Mode." The first three buttons areused to choose "reverse," "neutral,"or "drive" The up and down arrowsare used to move through the rangeof six forward gears in "drive," Thisis very similar to any otherautomatic transmission, but thetouch pad is much more than just aconventional gear selector. It is thecommunication link between thetransmission and the operator.

The “Mode” button is used toinvoke a special function that hasbeen programmed into the electroniccontrol unit (ECU). In motorhomes,this special function is almostalways the economy shift schedule

that shifts gears at lower rpm toprovide better fuel economy. This isan appropriate choice whentraveling on flat terrain. In situationswhere maximum power is required,such as climbing grades andutilizing maximum engine brakingcapabilities, the standard shiftschedule is preferred.

The touch pad has two digitaldisplays: “Select,” which shows thegear or range of gears chosen by theoperator, and ‘Monitor” whichindicates the current gear oftransmission operation. In addition,a “Mode On” light indicates that thesecondary mode has been chosen.

When the ignition is turned onthe “DO NOT SHIFT” light, usuallylocated on the dash, illuminatesmomentarily, accompanied byaudible tones (short beeps) comingfrom the shift selector. This tells theoperator that the indicator light isfunctioning. The “Select” digitaldisplay will read “N.” When theengine is started, the operator maychoose “reverse,” “drive,” or, usingthe up and down arrows, a range offorward gears. After the operatorselects “drive,” pushing the downarrow will change the “Select”display incrementally from 6

through 1. For example, you maywant to limit the range of forwardgears to 1 through 4 when driving inheavy traffic. (Additional operatingtips are provided with this article.)Holding the up or down arrow willscroll the numbers until the button isreleased or the highest or lowestnumber is displayed. Every selectionchange will be accompanied by a“beep’ sound, and a visual change inthe “Select” display. The “Monitor”display will indicate the gearcurrently operating.

In the event of a transmissionmalfunction, the “DO NOT SHIFT”light may illuminate. This will beaccompanied by 8 seconds of shortbeeps from the shift selector andindicates that shifts are beingrestricted. The “Select” display willnot be lit, and transmissionoperation, may be restricted. If thefailure allows limited operation, youcan proceed to find serviceassistance. During this time upshiftsand downshifts may be restricted.Anytime the “DO NOT SHIFT”lamp is lit, a diagnostic code will berecorded. To clear a temporary

“DO NOT SHIFT” light andrestore operation, take thefollowing steps: 1. Bring the vehicleto a stop at a safe location and applythe parking brake. 2. Simultaneouslypress the up and the down arrowsonce. On the lever-type selector,push the “Display Mode” buttononce to gain access to the diagnosticcode information. 3. Press and holdthe “Mode” button until a toneis heard, and then release thebutton.

The transmission may returnto normal operation. If thecondition is temporary, the“DO NOT SHIFT” light willnot come back on, and thetransmission will operatenormally. If the condition is nottemporary, the “DO NOT SHIFT”light may come back on. The type ofoperation permitted by the CPU willdepend on the type of condition.Under certain circumstances, a shiftfrom neutral to an operating rangemay not be permitted. This situationwill require immediate attention.

The up and down arrows are alsoused to gain access to the oil level

sensor, if present, and to enter thediagnostic display mode. Please notethat the selector is capable ofdisplaying two characters at onetime. One character will be shownon the "Select" display, and theother will appear on the "Monitor"display. For example, the fact thatthe oil level is okay will bedisplayed as follows:

The troubleshooting guide includedwith this article outlines theprocedure for gaining access to andinterpreting the display codes. Youmay benefit from having this guideon hand while you explore thefunctions of the shift selector.

For additional information,contact your local Allisondistributor or dealer. Check theYellow Pages for the locationnearest you.

Message Select Display Monitor Display

Oil Level 0 L

Pause — —

Okay 0 K