powershift trans and auto trans shifting and control Flashcards
what are the three control circuits
clutch application - torque converter and charging -transmission lubrication
what is the purpose of the priority valve in the transmission control circuit
to allow the shift selector valve to receive working pressure before sending oil downstream
what is the purpose of the torque inlet relief valve
to dump oil back to the trans sump during cold start up
what is the purpose of the lube pressure release valve
to dump oil back to the trans sump if lubricating pressure for the trans gears is exceeded
when towing a unit with a powershift transmission care must be taken because
when towing the unit the charge pump will not be lubricating the gears as they are turning
what must you do before towing a unit with power shift transmission
elevate the drive wheels - remove the drive axles - remove the drive line to prevent transmission rotation
speed selector spool
directs oil from the transmission charging pump to the speed clutches in the planetary transmission
modulation relief valve
controls the maximum clutch application pressure
load piston
controls the rate of pressure rise in the clutch pistons
what does clutch modulation do for the system
prevents shift shock and excessive slippage
what will send oil to the direction clutches in a planetary
direction selector spool
what will happen if coolant is allowed to enter the transmission with composite clutches
they will be destroyed
what is function on an automatic transmission will provide upshifts and down shifts in refrence to ground speed
governor circuit
what is governor pressure also used for
to apply and release the lock up clutch
what are the four methods to control shift dampening
orifice - modulation - trimmer - accumulator
where is an orifice used to control clutch dampening
on the release circuit
a trimmer valve is used in
the application circuit of the clutch
the three electronic transmission shift control systems are
input components - processing components - output components
when T/S a electronically controlled transmission one of the first checks to preform would be
power supply
the function of the modulator circuit is to
provide a signal pressure that is proportional to the position of the engine throttle - used to delay transmission shift points during wide open throttle operation
oil flow for the transmission control system operation is supplied by
a charging pump that is driven at engine speed
output devices that are responsible for causing speed and direction changes are
speed sensors
the hydraulic governor in an automatic transmission operates by balancing the centrifugal force of the governor flyweights against
governor pressure
before oil travels into the transmission lubrication circuit it will be
cooled and filtered
the function of the governor circuit in an automatic transmission is to
provide a hydraulic signal that is proportional to engine ground speed
if a clutch is released much more quickly than the next clutch to be applied during a shift the result is
a flare up of engine rpm and momentary free wheeling of machine until the next clutch is fully applied
momentary engine lugging and slowing of machine speed during shift indicates
releasing clutch that has not fully released before next clutch is applied
what are four functions of the ECU in an electronically controlled shift system
control upshifts and downshifts - control clutch modulation - provide diagnostic information - provide a warning to the operator when a malfunction has occurred
