TRANSFER CASE SHIFT EFFORT SERVICE PARTS & PROCEDURES

SUBJECT: HIGH TRANSFER CASE SHIFT EFFORT (SERVICE PARTS AND PROCEDURES)

VEHICLES AFFECTED: 1988-90 K1,K2,K3 EQUIPPED W/NEW PROCESS 241 TRANSFER CASE ---------------------------------------------------------

Some 1988-90 K-Trucks may experience high transfer case shift effort or blockouts when "shifting on the fly" from 2H to 4H under cold weather conditions (usually less than 0 deg Celcius, 32 deg Fahrenheit). This condition may be corrected by the installation of the synthetic 75W90 gear lube described in Service Bulletin #89-4-108. If the installation of this fluid does not result in a satisfactory shift effort, and "Easy Shift" package may be installed in the transfer case. This package was installed in production early in the 1990 model year and will provide reduced transfer case shift effort under cold weather conditions.

INVOLVED VEHICLES:

All 1988-90 Kl, K2, K3 trucks equipped with New Process 241 transfer case and built prior to the VIN Breakpoints listed below:

GMC CHEVROLET

Fort Wayne: LZ507928 LZ125644 Oshawa: L1504890 L1111094 Pontiac East: LE504245 LE115343

SERVICE PARTS INFORMATION:

The "Easy Shift" package consists of the following parts. All parts listed must be utilized in order to achieve the desired results. Parts must be ordered individually. Quantity Figure 1 Part Number Description Required Reference# ----------- ----------- -------- ---------- 15619496 Front Case Half 1 45 15633553 Sector W/Shaft 1 55 15633554 Mode Shift Fork 1 54 15633556 Poppet Plunger 1 70 15633557 Spring 1 71 15633558 Plug 1 68 14071849 O-Ring 2 47 & 69 15581915 Vent Pipe 1 Not Shown 14095609 Input Seal 1 42 14037958 Retainer 1 66 14095598 Range sector seal 1 67 15580381 Output front seal 1 72 15642510 Adapter gasket 1 Not shown

SERVICE PROCEDURE:

Disassembly of the Transfer Case After Removal from Vehicle.

- Clean the transfer case using a solvent and a stiff brush.

Remove or Disconnect as shown in Figures 1 and 2

1. Front output flange nut (77), washer (76), rubber sealing washer (75) and front output flange (74) from the front output shaft.

2. Indicator lamp switch (46) and O-ring seal (47).

3. Speedometer sensor (9) and seal.

4. Poppet screw (68), O-ring seal (69), poppet plunger (70) and poppet spring (71).

Mainshaft Extension and Oil Pump Housing

Remove or Disconnect as shown in Figures 1 and 2

1. Rear extension housing bolts (3) and rear extension (4).

2. Bearing retainer (snap ring) (5) from the mainshaft (19).

3. Pump retainer housing bolts (7). - Pump retainer housing bolts are shouldered.

4. Pump retainer housing (8) from the rear case half (17).

5. Retainer (snap ring) (10), speedometer tone wheel (11) and remaining retainer (snap ring) (10) from the mainshaft (19).

6. Case bolts (3) from the case halves.

- Note the two longer bolts and washers go into doweled case holes (33).

- Separate case halves, insert screwdrivers into the slot cast in the case ends and pry apart. Do not attempt to wedge the case halves apart at any point on the mating surfaces.

- Be careful not to damage the oil pump (12) (located in the rear case half) while removing the rear case half (17).

Internal Components - Remove or Disconnect ------------------- -------------------- Tools Required: J8092 drive handle J33832 bearing installer and remover

1. Fort shift spring (52).

2. Retainer (snap ring) (23) from the front output shaft (21).

3. Mainshaft (19)/drive sprocket (20), chain (58) and driven sprocket (22) as a unit. Mode shift fork (54) and shift rail (48) will be removed with the mainshaft.

4. Shift lever nut (63), washer (64), shift lever (65), plastic washer (66) and O-ring seal (67) from the front case half.

5. Range shift fork (51), range shift hub (34) and sector with shaft (55) from the planetary carrier (36). It is necessary to rotate the sector with the shaft (55) to obtain clearance when removing the range fork (51).

6. Input bearing retainer bolts (43) and input bearing retainer (44) from the front case half (45).

7. Retainer snap ring (41) from the input gear (38).

8. Planetary carrier (36) and the input gear (38) from the annulus gear (62) using a soft hammer.

9. Input bearing retainer (39) and input bearing (40).

10. Front output bearing retainer ring (snap ring) (60).

11. Front output bearing (61) from the front case half (45) using J33832, and J8092.

12. Seal (42) from the input bearing retainer (44) if it shows signs of damage.

Assemble - Install or Connect -------- ------------------ Tools required: J 36371 bearing installer J 36373 bearing installer

1. New seal - P/N #14985698 (42) into retainer (44) if it was removed in step 12 above.

2. Bearing (61) into the new front case half P/N #1561946 (45) using J 36371.

3. New front output shaft seal P/N #15580381 (72) to the new front case half (45).

4. Front output bearing retainer ring (snap ring) (60) to the new case half.

5. Input bearing (40) using J 36373 and input bearing retainer (39) to the new case half.

6. Planetary carrier (36) and the input gear (38) to the annulus gear (62) using a soft hammer.

7. Retainer snap ring (41) to the input gear (38). Input bearing retainer (44) and input bearing retainer bolts (43) to the new front case half (45).

- Apply RTV or equivalent on bearing retainer mating surfaces.

NOTICE: Do not block oil feed hole from case to bearing retainer.

- Apply Loctite 242(R) or equivalent on bearing retainer bolts.

- Tighten bolts to 19 N.m (14 ft.lbs.).

8. New sector with shaft P/N #15633553 (55) into new front case half.

9. New O-ring seal P/N #14095598 (67), new plastic washer P/N #14037958 (66), shift lever lever (65), washer (64) and nut (63) to the new sector with shaft (55)/new front case half.

10. Range shift hub (34) and range shift fork (51) into the planetary carrier (36). It is necessary to rotate the sector with shaft (55) to obtain clearance when installing the range fork (51).

11. Mainshaft (19)/drive sprocket (20), chain (58) and driven sprocket (22) as a unit. New mode shift fork P/N #15633554 (54) and shift rail (48) will be installed with the mainshaft.

12. Retainer (snap ring) (23) to the front output shaft (21).

13. Fork shift spring (52).

Mainshaft Extension and Oil Pump - Assemble

1. Rear case (17) over mainshaft (19) and onto the new front case half (45).

- Apply RTV sealer to the case mating surfaces.

- Be careful not to damage, the oil pump (12) while installing the rear case half.

2. Case bolts (3) into case halves.

- Transfer dowels from old case half to new case half it necessary.

- Apply Loctite 242(4) or equivalent on pump housing bolt threads.

- The two longer bolts and washers are used in the doweled case holes.

- Tighten bolts to 31 N.m (23 ft. lbs.).

3. Retainer (snap ring) (10), speedometer tone wheel (11) and remaining retainer (snap ring) (10) to the main shaft (19).

4. Pump retainer housing (8) and pump housing bolts (7) to the rear case half (17).

- Apply Loctite 242(4) or equivalent on pump housing bolts.

- Pump housing bolts (7) are shouldered.

- Tighten bolts to 41 N.m (30 ft.lbs.).

5. Bearing retainer (snap ring) (5), to the main shaft (19). 6. Rear extension housing (4) and extension housing bolts (3) to the pump retainer housing (8).

- Apply RTV sealer to the mating surfaces.

- Apply Loctite 242(R) or equivalent on the extension housing bolts.

- Tighten bolts to 31 N.m (23 ft.lbs.).

External Components - Install or Connect

1. New poppet plunger P/N #15633556 (70), new poppet spring P/N #15633557 (71), new O-ring seal P/N #14071849 (69), and new poppet screw P/N #15633558 (68) to the new front case half (45).

- Tighten poppet screw to 31 N.m (23 ft.lbs.).

2. Speedometer sensor (9) and seal to the pump retainer housing (8)

- Tighten sensor to 31 N.m (23 ft.lbs.).

3. Indicator lamp switch (46) and new o-ring P/N #14071849 (47) to the front case housing.

- Tighten switch to 24 N.m (17 ft. lbs.).

4. Front output flange (74), rubber sealing washer (75), washer (76) and flange nut (77).

- Tighten nut (26) to 149 N.m (110 ft.lbs.).

5. New vent pipe P/N #15581915 in new front case half.

- Lightly coat end of vent pipe with Loctite 609(R) or equivalent.

6. Reinstall transfer case in vehicle using new adapter gasket P/N.#1564210.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.