The driver selects a particular gear by moving the
shift lever to the desired gear position. This move-
ment moves the internal transmission shift compo-
nents to begin the shift sequence. As the shift lever
moves the selected shift rail, the shift fork attached
to that rail begins to move. The fork is positioned in
a groove in the outer circumference of the synchro-
nizer sleeve. As the shift fork moves the synchronizer
sleeve, the synchronizer begins to speed-up or slow
down the selected gear (depending on whether we are
up-shifting or down-shifting). The synchronizer does
this by having the synchronizer hub splined to the
mainshaft, or the countershaft in some cases, and
moving the blocker ring into contact with the gear’s
friction cone. As the blocker ring and friction cone
come together, the gear speed is brought up or down
to the speed of the synchronizer. As the two speeds
match, the splines on the inside of the synchronizer
sleeve become aligned with the teeth on the blocker
ring and the friction cone and eventually will slide
over the teeth, locking the gear to the mainshaft, or
countershaft, through the synchronizer.
DIAGNOSIS AND TESTING - MANUAL
TRANSMISSION
LOW LUBRICANT LEVEL
A low transmission lubricant level is generally the
result of a leak, inadequate lubricant fill, or an incor-
rect lubricant level check.
Leaks can occur at the mating surfaces of the gear
case, intermediate plate and adaptor or extension
housing, or from the front/rear seals. A suspected
leak could also be the result of an overfill condition.
Leaks at the rear of the extension or adapter hous-
ing will be from the housing oil seals. Leaks at com-
ponent mating surfaces will probably be the result of
inadequate sealer, gaps in the sealer, incorrect bolt
tightening, or use of a non–recommended sealer.
A leak at the front of the transmission will be from
either the front bearing retainer or retainer seal.
Lubricant may be seen dripping from the clutch
housing after extended operation. If the leak is
severe, it may also contaminate the clutch disc caus-
ing the disc to slip, grab, and/or chatter.
A correct lubricant level check can only be made
when the vehicle is level. Also allow the lubricant to
settle for a minute or so before checking. These rec-
ommendations will ensure an accurate check and
avoid an underfill or overfill condition. Always check
the lubricant level after any addition of fluid to avoid
an incorrect lubricant level condition.
HARD SHIFTING
Hard shifting is usually caused by a low lubricant
level, improper, or contaminated lubricants. The con-
sequence of using non–recommended lubricants is
noise, excessive wear, internal bind, and hard shift-
ing. Substantial lubricant leaks can result in gear,
shift rail, synchro, and bearing damage. If a leak
goes undetected for an extended period, the first indi-
cations of component damage are usually hard shift-
ing and noise.
Component damage, incorrect clutch adjustment, or
a damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect
adjustment or a worn/damaged pressure plate or disc
can cause incorrect release. If the clutch problem is
advanced, gear clash during shifts can result. Worn or
damaged synchro rings can cause gear clash when
shifting into any forward gear. In some new or rebuilt
transmissions, new synchro rings may tend to stick
slightly causing hard or noisy shifts. In most cases,
this condition will decline as the rings wear–in.
TRANSMISSION NOISE
Most manual transmissions make some noise dur-
ing normal operation. Rotating gears generate a mild
whine that is audible, but generally only at extreme
speeds.
Severe, highly audible transmission noise is gener-
ally the initial indicator of a lubricant problem.
Insufficient, improper, or contaminated lubricant will
promote rapid wear of gears, synchros, shift rails,
forks and bearings. The overheating caused by a
lubricant problem, can also lead to gear breakage.
REMOVAL
(1) Disconnect battery negative cable.
(2) Shift transmission into Neutral.
(3) Remove floor console. Refer to Group 23 Body
for proper procedures.
(4) Remove shift lever boot.
(5) Remove the shift lever extension from the shift
tower and lever assembly.
(6) Raise vehicle.
(7) Remove skid plate, if equipped (4WD).
(8) If transmission will be disassembled for repair,
remove drain plug and drain lubricant from trans-
mission.
(9) Mark propeller shafts and companion flange for
assembly reference.
(10) Disconnect and remove propeller shafts.
(11) Disconnect and remove exhaust system Y-pipe.
Then disconnect and lower remaining exhaust pipes
for clearance as necessary.
(12) Disconnect backup light switch wires.
2WD
(1) Remove bolts/nuts attaching transmission to
rear mount.
(2) Support transmission with a transmission jack.
Secure transmission to jack with safety chains.
21 - 36
MANUAL - NV3500
AN
MANUAL - NV3500 (Continued)