• Increased service life a nd relia bility.
• Lower mainten ance cost s.
TRANSMISSION IDENTIFICATION
The transmission can be gen erica lly identified
visually by the pr esence of a r ound 13-wa y connector
locat ed near t he fr ont corner of th e tr ansmission oil
pa n, on th e right side. Specific tra nsmission inform a-
tion can be found stamped into a pad on th e left side
of the tra nsmission, above th e oil pan ra il.
TRANSMISSION GEAR RATIOS
The gear ratios for th e NAG1 a utomatic tra nsmis-
sion are as follows:
1st Gea r ............................3.59:1
2n d Gea r ............................2.19:1
3r d Gea r ............................1.41:1
4t h Gea r ............................1.00:1
5t h Gea r ............................0.83:1
Rever se .............................3.16:1
TRANSMISSION HOUSING
The convert er h ousing and tra nsmission a re ma de
from a light alloy. These are bolted t ogeth er a nd cen-
tered via the ou ter multi-disc car rier of m ulti-disc
holding clutch, B1. A coated in term ediate plate pr o-
vides the sealing. The oil pu mp a nd t he outer multi-
disc ca rrier of the multi-disc holding clutch , B1, a re
bolted t o th e conver ter housing. Th e st ator sha ft is
pr essed int o it and prevent ed from rotating by
splines. The electroh ydrau lic unit is bolted to the
transmission housing from u ndernea th. A sheet
meta l steel oil pan forms the closure.
MECHANICAL SECTION
The m echan ical section consists of a input sha ft,
output shaft , a sun gear shaft , a nd th ree planet ary
gear sets which are coupled t o each ot her. The plan-
etar y gea r sets each h ave four plan etar y pinion
gear s. The oil pressur e for the torqu e converter
lock-up clu tch and clutch K2 is supplied through
bores in t he in pu t sh aft. The oil pressu re to clutch
K3 is tra nsmit ted through t he outpu t shaft. The
lubr icat ing oil is distribut ed thr ough additional bor es
in both sha fts. All th e bearing poin ts of the gear sets,
as well as the freewheeling clutch es an d actuator s,
are supplied with lu brica ting oil. Th e pa rking lock
gear is connected to the ou tput sha ft via splines.
Freewheeling clutches F1 a nd F2 a re used to opt i-
mize the shifts. The front freewh eel, F1, is support ed
on th e extension of the sta tor sh aft on t he tra nsmis-
sion side and, in the locking direction, connect s the
su n gear of the front planetary gea r set to the t rans-
mission housing. In the locking dir ection , the rear
freewh eeling clut ch, F2, connects th e sun gear of t he
center pla neta ry gear set to the su n gear of the r ear
plan etar y gear set.
ELECTROHYDRAULIC CONTROL UNIT
The electr ohydra ulic control u nit comprises the
sh ift plat e m ade from light alloy for the hydr aulic
control and a n electr ical con trol unit. Th e electr ical
control un it comprises of a support ing body made of
plastic, in to which th e electrical components a re
assembled. The supporting body is mounted on the
sh ift plat e and screwed to it.
St rip condu ctors insert ed in to the supporting body
make t he con nection between th e electrical compo-
nent s a nd a plug connector. The con nection to t he
wiring h arness on t he vehicle an d the tr ansmission
control module (TCM) i s produced via this 13-pin
plug connector wit h a bayon et lock.
SHIFT GROUPS
The hydrau lic cont rol compon ents (includin g actua-
tors) which a re r esponsible for the pressur e dist ribu -
tion before, during, a nd aft er a gear change are
descr ibed as a shift grou p. Ea ch shift group conta ins
a comma nd valve, a h olding pressur e shift valve, a
sh ift pressure shift valve, overlap r egulating valve,
and a solenoid.
The hydra ulic system contains three sh ift groups:
1-2/4-5, 2-3, and 3-4. Ea ch shift grou p can also be
descr ibed a s being in on e of two possible stat es. The
active shift gr oup is described a s being in the shift
ph ase wh en it is a ctively engaging/disengaging a
clutch combination. Th e 1-2/4-5 shift group control
the B1 and K1 clut ches. The 2-3 shift group cont rols
the K2 a nd K3 clutches. The 3-4 shift group con trols
the K3 and B2 clut ches.
OPERATION
The tran sm ission cont rol is divided into th e elec-
tronic and hydr aulic tra nsmission control functions.
While the elect ronic t ransmission cont rol is responsi-
ble for gear selection and for m atching the pressures
to the torque to be tr ansmitted, th e t ransmission’s
power su pply con trol occurs via hydrau lic elemen ts
in the electroh ydraulic con trol module. Th e oil supply
to th e hydraulic elemen ts, such a s the h ydrodyn amic
torqu e converter, the shift element s and th e hydrau -
lic tran sm ission cont rol, is provided by way of an oil
pu mp connected with th e torque convert er.
The Transm ission Contr ol Module (TCM) allows for
the pr ecise adapta tion of pressures to the correspond-
ing operatin g conditions and t o the engine out pu t
du ring th e gearshift phase, resultin g in a noticeable
improvement in shift qu ality. The engine speed limit
can be rea ched in th e individu al gears at fu ll throt tle
and kickdown. The shift range can be cha nged in the
forwar d gears while driving, but the TCM employs a
downshift safeguard to prevent over-revving th e
engine. The system offer s the addition al a dvantage of
21 - 4 AUTOMATIC TRANSMISSION NAG1 - SERVICE INFORMATION VA
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