Diagnosis Of The Transfer Case; On-Vehicle Service; Maintenance And Adjustment - GMC G Service Manual

7D2-4 208 TRANSFER CASE

DIAGNOSIS OF THE TRANSFER CASE

Before repairing a suspected transfer case problem,
check the driveline components. The problem may be
PROBLEM
Ttansfer Case Difficult
To Shift Or Will Not
Shift Into Desired
Range
Transfer Case Noisy
In All Drive Modes
Noisy In — Or Jumps
Out Of Four Wheel
Drive Low Range
Lubricant Leaking
From Output Shaft
Seals Or From Vent
Abnormal Tire Wear

MAINTENANCE AND ADJUSTMENT

CASE-OIL CHANGE
H
Remove or Disconnect
• Raise the vehicle.
• Position a drain pan under the transfer case.
1. Fill plug.
2. Drain plug.
• Drain the lubricant.
POSSIBLE CAUSE
1. Vehicle speed is too great to permit shifting.
2. If the vehicle was operated for extended peri­
od in the 4H mode on dry paved surface,
driveline torque load may cause difficult
shifting.
3. Transfer case external shift linkage is
binding.
4. Insufficient or incorrect lubricant.
5. Internal components binding, worn or
damaged.
1. Insufficient or incorrect lubricant.
1. Transfer case is not completely engaged in
4L position.
2. Shift linkage is loose or binding.
3. Range fork cracked, inserts worn, or fork is
binding on shift rail.
4. Annulus gear or lockplate is worn or
damaged.
1. Transfer case overfilled.
2. Vent closed or restricted.
3. Output shaft seals damaged or installed
incorrectly.
1. Extended operation on dry hard surface
(paved) roads in 4H range.

ON-VEHICLE SERVICE

related to the front hubs, axles, propeller shafts, wheels and
tires, transmission or clutch.
CORRECTION
1. Stop the vehicle and shift into the desired
range. Or reduce the speed to 2-3 mph (3-4
km/h) before attempting to shift.
2. Stop the vehicle, shift the transmission to
neutral, shift the transfer case to 2H mode
and operate the vehicle in 2H on dry paved
surfaces.
3. Lubricate, repair or replace linkage, or tight­
en loose components as necessary.
4. Drain and refill to the edge of the fill hole with
DEXRON® II.
5. Disassemble the unit and replace worn or
damaged components as necessary.
1. Drain and refill to the edge of the fill hole with
DEXRON® II. Check for leaks and repair if
necessary. If unit is still noisy after draining
and refilling, disassemble and inspect to lo­
cate the source of the noise.
1. Stop the vehicle, shift the transfer case into
Neutral, then shift back into the 4L position.
2. Tighten, lubricate or repair linkage as
necessary.
3. Disassemble the unit and repair as
necessary.
4. Disassemble the unit and repair as
necessary.
1. Drain to the correct level.
2. Clear or replace the vent if necessary.
3. Replace seals. Be sure seal lip faces interior
of case when installed. Also be sure flange
seal surfaces are not scored or nicked. Re­
move scores, nicks with fine sandpaper or
replace the flange if necessary.
1. Operate in 2H on hard surface (paved)
roads.
Install or Connect
1. Drain plug.
Tighten
• Plug to 47 N«m (35 ft. lb.).
• Remove the drain pan.
• Fill the transfer case to the edge of fill plug
opening with DEXRON® II.
2. Fill plug.
Tighten
• Plug to 47 N-m (35 ft. lb.).
• Lower the vehicle.
GMTB-0886-2L