Jeep Cherokee 1999 Electronic Service Manual page 1399

21 - 76 TRANSMISSION AND TRANSFER CASE
GEN ERAL I N FORM AT I ON (Cont inue d)
Fig. 2 Transmission Part And Serial Number
TORQUE CONVERTER—ELECTRONIC CLUTCH
Th e t or qu e con ver t er is a h ydr a u lic device t h a t
cou ples t h e en gin e cr a n ksh a ft t o t h e t r a n sm ission .
Th e t or qu e con ver t er con sist s of a n ou t er sh ell wit h
a n in t er n a l t u r bin e, a st a t or, a n over r u n n in g clu t ch ,
a n im peller a n d a n elect r on ica lly a pplied con ver t er
clu t ch . Tor qu e m u lt iplica t ion is cr ea t ed wh en t h e st a -
t or dir ect s t h e h ydr a u lic flow fr om t h e t u r bin e t o
r ot a t e t h e im peller in t h e dir ect ion t h e en gin e cr a n k-
sh a ft is t u r n in g. Th e t u r bin e t r a n sfer s power t o t h e
pla n et a r y gea r set s in t h e t r a n sm ission . Th e t r a n sfer
of power in t o t h e im peller a ssist s t or qu e m u lt iplica -
t ion . At low veh icle speed, t h e over r u n n in g clu t ch
h olds t h e st a t or (du r in g t or qu e m u lt iplica t ion ) a n d
a llows t h e st a t or t o fr ee wh eel a t h igh veh icle speed.
Th e con ver t er clu t ch pr ovides r edu ced en gin e speed
a n d gr ea t er fu el econ om y wh en en ga ged. Clu t ch
en ga gem en t a lso pr ovides r edu ced t r a n sm ission flu id
t em per a t u r es. Th e con ver t er clu t ch en ga ges in t h ir d
gea r. Th e t or qu e con ver t er h u b dr ives t h e t r a n sm is-
sion oil (flu id) pu m p.
Th e t or qu e con ver t er is a sea led, welded u n it t h a t
is n ot r epa ir a ble a n d is ser viced a s a n a ssem bly.
CAUTION: The torque converter must be replaced if
a transmission failure resulted in large amounts of
metal or fiber contamination in the fluid. If the fluid
is contaminated, flush the fluid cooler and lines.
TRANSMISSION GEAR RA TIOS
F or wa r d gea r r a t ios a r e:
• 2.74:1 (fir st gea r )
• 1.54:1 (secon d gea r )
• 1.00:1 (t h ir d gea r )
Location
GEARSHIFT MECHANISM
Th e sh ift m ech a n ism is ca ble oper a t ed a n d pr o-
vides six sh ift posit ion s. Th e sh ift in dica t or is loca t ed
on t h e con sole n ext t o t h e gea r sh ift . Th e sh ift posi-
t ion s a r e:
• P a r k (P )
• Rever se (R)
• Neu t r a l (N)
• Dr ive (D)
• Ma n u a l Secon d (2)
• Ma n u a l Low (1)
Ma n u a l low (1) r a n ge pr ovides fir st gea r on ly. Over
r u n br a kin g is a lso pr ovided in t h is r a n ge. Ma n u a l
secon d (2) r a n ge pr ovides fir st a n d secon d gea r on ly.
Dr ive r a n ge pr ovides fir st , secon d, a n d t h ir d gea r
r a n ges.
DESCRI PT I ON AN D OPERAT I ON
HYDRAULIC CONTROL SYSTEM
Th e t r a n sm ission h ydr a u lic con t r ol syst em per-
for m s fou r ba sic fu n ct ion s.
• pr essu r e su pply
• pr essu r e r egu la t ion
• flow con t r ol a n d lu br ica t ion
• clu t ch /ba n d a pplica t ion
PRESSURE SUPPL Y
Th e oil pu m p develops flu id pr essu r e for clu t ch /
ba n d a pplica t ion a n d for lu br ica t ion . Th e pu m p is
dr iven by t h e t or qu e con ver t er. Th e con ver t er is
dr iven by a dr ivepla t e a t t a ch ed t o t h e en gin e cr a n k-
sh a ft .
Pressure Regulation
Th e pr essu r e r egu la t or va lve m a in t a in s lin e (oper-
a t in g) pr essu r e. Th e a m ou n t of pr essu r e developed is
con t r olled by t h r ot t le pr essu r e wh ich is depen den t on
t h e degr ee of t h r ot t le open in g. Th e r egu la t or va lve is
loca t ed in t h e va lve body.
Th e t h r ot t le va lve det er m in es t h r ot t le pr essu r e
a n d sh ift speed. Gover n or pr essu r e in cr ea ses in pr o-
por t ion t o veh icle speed. Th e t h r ot t le va lve con t r ols
u psh ift a n d down sh ift speeds by r egu la t in g pr essu r e
a ccor din g t o t h r ot t le posit ion .
Flow Control And Lubrication
Th e m a n u a l va lve is oper a t ed by t h e gea r sh ift lin k-
a ge a n d pr ovides t h e oper a t in g r a n ge select ed by t h e
dr iver.
Th e swit ch va lve con t r ols lin e pr essu r e t o t h e con -
ver t er clu t ch . Th e va lve a lso dir ect s oil t o t h e coolin g
a n d lu br ica t ion cir cu it s. Th e swit ch va lve r egu la t es
oil pr essu r e t o t h e t or qu e con ver t er by lim it in g m a x-
im u m oil pr essu r e t o 130 psi.
X J