Allison Transmission 3200 SP User Manual

active,theshiftpointsforupshiftsareraisedinordertoholdthetransmission
initscurrentgearandinhibitupshiftingbeyondthecurrentrange.Holdsare
activatedbyselectingthecurrentrangeoralowerrangeontheshiftselector.
CAUTION:Atypicaluseofthe"hold"featureistomaximizeengine
brakingwhenoperatingdownhill.However,inordertoprevent
over-speedingtheengine,theholdfunctionisnotinnite.Itwill
permitshiftsfromtheholdrangetothenexthigherrangeatsome
speedabovetheshiftcalibrationspeed.
4.2.2DOWNSHIFTING.Downshiftsareallowedtooccuraslongas
transmissionoutputspeedislowenoughtokeepfromover-speedingthe
engineaftercompletingthedownshift.Whenarangedownshiftismanually
selectedbytheoperator,butthetransmissionoutputspeedisdeterminedto
beabovethelimits,thetransmissionremainsintherangeeventhougha
lowerrangewasrequestedbytheoperator.Ashifttoalowerrangecanoccur
whentheoperatorappliesthevehicleservicebrakesoraretardingdevice,
suchasanexhaustbrake,enginebrake,orretarder.Thisactionreducesthe
transmissionoutputspeedwhichinturnlowersthevehiclespeed,allowing
thetransmissiontoshifttothelowerrange.
4.2.2.1PRESELECTSCHEDULEFORDOWNSHIFTS
Thepreselectdownshiftscheduleissimilartotheholdfeature.Theoperator
mayinitiatethepreselectdownshiftshiftschedulebyselectinganyforward
gearontheshiftselectorthatislowerthanthegearcurrentlyinuse.Whena
rangehasbeen"preselected"inthismanner,shiftstoandfromgearsabove
thepreselectedgearrangeoccurathigherthannormalenginespeeds.Shifts
belowthepreselectedrangearenotaffected.
Preselectdownshiftingisbenecialinmaintaininghigherenginespeed,
resultinginincreasedenginebrakingorenginebrakeperformanceduring
downhilloperationorvehicledecelerationcycles.However,preselectshifts
arepermittedonlyifanengineover-speedconditionwillnotoccurafter
completionofthedownshift.
NOTE:Preselectingduringnormaloperationmayresultinreduced
fueleconomy.
4.2.2.2NON-ENGINEBRAKEOPERATION
Twochoicesofpreselectshiftschedulesareavailableforgoverning
preselecteddownshiftsduringnormaltransmissionoperation.Oneofthe
61

Allison Transmission 3200 SP Specifications

General

Enclosure Rating	IP67
Input Voltage	12/24 VDC
Operating Temperature Range	-40°C to +85°C
Communication Protocol	SAE J1939
Memory	Flash and EEPROM
Diagnostic Capabilities	fault code logging
Dimensions	Varies by model
Weight	Varies by model
I/O	Digital and Analog Inputs/Outputs
Type	Transmission Electronic Control Unit (TECU)