THE AUTOMATIC TRANSJ\IISSION Neutral a nd park T he front and rear clutches are off, a nd no power is transm itt ed fro m the converter to the gear set. The fron t a nd rea r bands a re als o released, excep t in ' P', where for co ns truct ional reasons th e rea r band is applied as
long as the engine is runnin g.
hydraulic requirements, thu s enabling the engine to be started t hro ugh the tran smi ssion .
Section FFF(b).7 GO YE R='O R
Section FFF(b).4 HYDR AULI C SYSTE :\1 T he hydraulic system contains a front and rea r pump. both of th e internal /external gear pa ttern, picking up fluid fro m the oil pan th rough separate stra iners. Shift control is provided by a centrifuga lly o pera ted hydra ulic governor o n the tra nsm ission output ...ha ft. This governor works in co njunct io n with va lves in the valve bod ies assembl y located in th e base o f the tra nsmi ssion . These va lves regulate fluid pr essure and direct it to appropriate tr a nsmissio n component s. Fi g. F F F(b).9 shows a sim plified dia gram of the system whi lst Sect ion F F F(b).8 explains and illus t rates the hydrauli c circuit operation in each of the gears and for 'N' and 'P' ,
Section FFF(b).5 FRO NT I' Ul\lI' T he fro nt pu m p, d riven by t he conve rte r im peller, is in operatio n wheneve r the engine is running. This pu mp, thr ou gh the primary and seconda ry regula tor valves, supplies t he hyd raulic requiremen ts o f the transmiss ion with t he engi ne running when the vehicle is sta tionary, as well as at low vehicle spee ds before the rear pump becomes effective. When the rear pump is effective th e front pump check valve closes, but a by-pass permits t he pum p to still supply the conve rte r and lubrica tion requirements in conj un cti on with th e rea r pu mp ; it th en operates a t the reduced p ress ure regulat ed by the seco ndary regul at or valve. exce ss flow exhausti ng to inlet and thu s m inimizing pump losses.
Section FFF(b).6 REAR PUMP Th e rear pump is dr iven by the d riven shaft of the tr an smi ssio n. 11 is fully effective at speed s above 20 m.p.h, (32 km. p.h.) approximately and then supplies t he hyd raulic requirements of the tran smis sion, If, due to a dead en gine, the front pump is inoperative, the rear p ump, above 20 m.p.h. (32 km.p.h .), can provide all Magnette (Mark IV) and 4JSe\ enty Two.
Issue 3.
55274
T he go ve rno r, revolving wit h the driven sha ft. is basicall y a pre ssu re-reg ulating valve which red uces line pre ssure to a valu e t hat va ries with driven shaft (i.e . vehicle ) speed , This va ria ble pre ssure is utilized in the control system to effect up- a nd d own- shi fts through the 1-2 and 2-3 shift valve s, Rotation of the gove rnor a t low speeds cau ses the governor weigh t an d valve to pro d uce a centrifugal force. T his outward force is opposed by an equal and opposite hydraulic for ce produced by governor pressu re ac t ing up on a sma ll area oft he governor val ve. Because the go verno r va lve is a regulati ng val ve an d will a ttem pt to remain in equilibrium. governor pressure '" ill rise in accordance with the increase in centrifugal force cau sed by increased ro tati onal speed. As speed increases, the governo r weight moves ou twa rds to a stop in the governo r body , when it ca n m ove no farther. When this occurs a spring located bet ween the weight and the governo r valve becom es effec tive. The constan t force of this spring t hen combines with the centrifugal for ce of the governor valve, the total t he n being opposed by governor pre ssure, th us rendering governor pre ssure less sensitive to ou tput sha ft speed va riations. Thus. the govern or provides two dis tinct phases o f regu latio n. the first being used fo r accu rate co ntrol of th e lo w-speed shift po ints.
Section FFF(b).8 CO'lT RO L SYSTE ;\I
1 he co ntrol system utilizes three ba sic types o f va lve: regulati ng valves, shutt le val ves. and a manual valve. Pressure con tro l is pro vided by th e p rimary a nd seco ndary reg ulato r valve s, thc fo rmer opera t ing in conjunction with th rottle pr essure acting upon t he sp ring end and modulated t hrott le pressure acting on the opposite end, Shi ft control is provided by 1-2 an d 2-3 shi ft val ves operated by governor pre ssure acting upo n one end an d throttle pre ssure ac ting up on t he spring end, line pre ssure acting up on differential areas pr ovidi ng shi ft spee d hysteresis. Ma nu a l co nt ro l is pr ovided by the man ual cont rol va lve, which , accordi ng to t he pos itio n of th e selecto r, directs fluid to or pr ovides an exhau st for clu tch and servo piston s. i'OT E.-For case of refer ence all hydraulic circuits are identified by' numbers (sec diagram] which arc listed on pag e FfF(h).19. FFF(b ).7