( 1987 GMC Jimmy 4 Wheel Drive 350 Engine 5.7 liter ) ( had rebuilt transmission, torque converter and replaced transfer case) . Problem is that the transmission slipps out of gear / into neautral only when breaking abruptly. To get it back into 2 wheel drive I need to switch into 4 wheel drive ( take it out of 4 wheel drive ) then it operates fine. Replaced engine mounts and took it back in for service 3 times for linkage adjustment and still has the problem but not as frequiently. Can you provide me any advise? It's frustrating!

Are the vacuum lines properly connected and have vacuum available to the switch?

4 wheel drive 4.3 liter engine?

The simple answer is to replace the TCCM (transfer case control module).
Being both cheap and inquisitive, I wanted to investigate further, and I will provide a more in-depth answer.

This answer pertains to various GM vehicles. These include the Chevy Blazer, GMC Jimmy, S10, S15, Sonoma vehicles from 1999, 2000, 2001, 2002, 2003, 2004, & 2005.
Specifically the 15748800 module for the NP8 option 4 button automatic 4X4 NVG-236/246 transfer case.

I doing research online, I find that 15154323 might be an alternate TCCM, and that GM redesigned the module and now sells the replacement for this module with a 12577412 part number for about $300.

This information refers to the 15748800 module.
Symptoms. If the vehicle is started and driven in 2 hi, the vehicle operates normally.
If the driver attempts to switch the transfer case into any other mode, the transfer case makes noise as it shifts, the service 4x4 light comes on and the newly selected mode indicator light starts to flash.

The TCCM is mounted behind the passenger side kick panel cover. It should be removed but left connected. Pin F4 should be monitored with either a lamp or meter. This pin should be high or 12 volts when in 2 wheel drive, and low or ground when in 4 wheel drive.
A quick test of the system is to ground the F4 pin, recycle the ignition, and try shifting the transfer case into and out of 4 wheel drive. ( I used a lamp based test light to be safe. Do not an LED based one.) If the mode indicator light remains steady and the Service 4X4 does not light, proceed with this repair procedure. If this does not resolve the issue, please proceed to troubleshoot the front vacuum system, 4X4 solenoid, 4X4 actuator, front axle, or front axle indicator switch.

If this test appears to resolve the issue, you will need to remove the TCCM module from the vehicle. Bend the 8 tabs away from the back cover. Remove the top cover, unscrew the board from the back cover / plate. turn over the board at a static safe work station, and measure the indicated 10,000 ohm SMD resistor. In this module, the resistor is required to operate near it's limits, and I believe that the conformal coating trapped heat and caused the resistor to fail. You can check other resistors nearby for a relative comparison. If found to be open, the resistor can be replaced with a higher power value 10,000 ohm SMD resistor, or a conventional 10,000 ohm resistor with wired leads.

The TCCM should be checked for corrosion on the connectors and cleaned if nessacary. The module can then be restored to the vehicle, and your 4X4 should work normally.

Please respond if this procedure helps you.

Front view / pin side
f16f1 Connector Part Information1205210716 Way F Micro-Pack 100 Series (ORN) Pin Wire Color Circuit No. Function
E1 Tan 1569 Transfer Case Lock Soleniod Output
E2 - - Not Used
E3 PNK 1561 AWD/4WD Indicator Lamp Output
E4 Lt GRN/BLK 1563 2 HI Indicator Lamp Output
E5 BRN/WHT 1555 Transfer Case Position Switch Encoder Signal
E6 RED/WHT 1556 Transfer Case Position Switch Encoder Signal
E7 YEL/BLK 1558 Transfer Case Position Switch Encoder Signal
E8 DK BLU/WHT 1557 Transfer Case Position Switch Encoder Signal
E9 DK GRN/WHT 1133 Class 2 Serial Data Signal
E10 BRN 241 Fuse Output - Ignition 3 - Type III Fuse
E11 PPL 806 Fuse Output - Crank - Type III Fuse
E12 YEL 400 Vehicle Speed Sensor Signal
E13 PPL 401 Vehicle Speed Sensor Return
E14 BLK/WHT 1695 Four Wheel Drive Front Wheel Lock Telltale
E15 - - Not Used
E16 BLK/WHT 451 Engine Control Module Ground
F1 PPL/WHT 1565 4 LO Indicator Lamp Output
F2 TAN/BLK 1566 4 HI Indicator Lamp Output
F3 BRN 1560 Neutral Indicator Lamp Output
F4 GRA/BLK 1570 Front Axle Actuator Output
F5 LT BLU 2221 Vehicle Speed Sensor Signal
F6 DK GRN 2222 Vehicle Speed Sensor Return
F7 GRA/BLK 1694 Four Wheel Drive Switch Signal - Low
F8 - F11 - - Not Used
F12 BLK/WHT 1554 Transfer Case Encoder Signal Return
F13 LT GRN/BLK 431 Reference Voltage Feed - 8 Volt Reference
F14 LT GRN/BLK 431 Reference Voltage Feed - 8 Volt Reference
F15 - - Not Used
F16 LT BLU 1693 Four Wheel Drive Switch Signal
Front view / pin side

Connector Part Information120528564 Way F Metri-Pack 280 Series (BLK) Pin Wire Color Circuit No. Function
A BLK 1552 Transfer Case Motor Feed - Clockwise
B RED 1553 Transfer Case Motor Feed - Counterclockwise
C BLK 1050 Ground
D ORG 1640 Fuse Output - Battery - Type III Fuse

If you have the push buttons on the dash board you must follow the instructions in your owners manual to return the transfer case to 2wd from neutral. I don't remember for sure but I think you must have the transmission in neutral, foot on brake, press and hold both 2wd and 4wdlow buttons at same time. My father who lives 45 miles from me has the Jimmy, I don't. Hope this helps, Jim

No, the jimmy has a much smaller tranny.

when changing the filter? maybe 4, at overhaul maybe 10-11?

2000 TOYOTA TACOMA 2.7L 4-cyl Engine Code 3RZ-FE

Engine Oil Grade 1......API* All TEMPS......5W-30 Optional ..10W-30
Engine, 2WD, with filter..........5.5 liters
Engine, 4WD, with filter..........5.4 liters

Manual Transmission,......GL-5/ GL-4 All TEMPS......75W-90
Automatic Transmission,A340E......AF3 / A43D......AF3

Differential, Front/ Rear W/ ADRD......GL-5 ALL TEMPS......75W-90
Differential, Front Less ADRD......GL-5 ALL TEMPS......80W-90

Transfer Case,......GL-4/GL-5 ALL TEMPS......75W-90 Gear oil.

Capacity:
Cooling System, Initial Fill..........8.5 liters
Automatic Transmission, A340E Initial Fill..........1.6 liters
Automatic Transmission, A340F Initial Fill..........2 liters
Automatic Transmission, A43D Initial Fill..........2.4 liters
Automatic Transmission, Total Fill
4 speed A340E..........7.2 liters
4 speed A340F..........10.1 liters
4 speed A43D..........6.5 liters
Manual Transmission, ..........2.5 liters
Differential, With ADRD Front..........1.2 liters
Differential, Without ADRD Front..........1.1 liters
Differential, 2WD V6 Rear..........2.6 liters
Differential, 4WD Extra Long Rear..........2.5 liters
Differential, Short WB With LSD Rear..........2.7 liters
Differential, Short WB Without LS Rear..........2.6 liters
Transfer Case, Electronic..........1.2 liters
Transfer Case, STD..........1 liters

1. Disconnect the battery negative cable.
2. Raise the vehicle. Support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
3. Disconnect the range selector cable from the transmission bracket and from the transmission range select lever. Refer to Shift Cable Replacement .
4. Remove the rear propeller shaft. Refer to Rear Propeller Shaft in Propeller Shaft.
5. Support the transmission with a transmission jack.
6. Remove the transfer case if equipped. Refer to the appropriate Transfer Case Replacement in Transfer Case:
• Transfer Case Replacement (Selectable Four Wheel Drive) . • Transfer Case Replacement (Auto Four Wheel Drive ) . • Transfer Case Replacement (Manual Four Wheel Drive) .



7. Gasoline Engine--Remove the following components:
7.1. Two bolts 7.2. Two washers 7.3. One nut 7.4. The transmission to engine brace



8. Diesel Engine--Remove the following components:
8.1. Two bolts 8.2. Two washers 8.3. One nut 8.4. The transmission to engine brace
9. Remove the transmission rear mount.
10. Remove the frame crossmember.
11. Remove the exhaust pipe from the exhaust manifolds. Remove the muffler assembly from the exhaust pipe, if required. Refer to Exhaust System.




12. For the 5.0L Gasoline Engine: Remove the six bolts securing the converter cover to the transmission.
13. Remove the starter. Refer to Starter Replacement in Engine Electrical.
14. For the 4.3L Gasoline Engine: Remove the dust plug at the end of the starter mounting port in order to gain access to the converter bolts.




15. For the Diesel Engine and 7.4L/5.7L Engines: Remove the four bolts securing the converter cover to the transmission.
16. Mark the flywheel and the torque converter alignment.




17. Remove the bolts that attach the torque converter to the engine flywheel.




18. Remove the transmission vent hose.
19. Disconnect the wiring harness connectors from the vehicle speed sensors and from the park neutral position switch.
20. Remove all vehicle electrical harness wires, harness clips, tubes, and brackets that may interfere with the removal of the transmission.
21. Remove the fluid fill tube and the fill tube seal from the transmission. Refer to Filler Tube Replacement .
22. Plug the fluid fill tube opening in the transmission.
23. Disconnect the transmission oil cooler pipes from the transmission. Refer to the oil cooler pipe quick connect fittings removal procedure in Oil Cooler Hose/Pipe Replacement .
24. Plug the transmission oil cooler pipe connectors in the transmission case.
25. Install the J 21366 in order to keep the torque converter from sliding off of the transmission turbine shaft.
26. Support the engine with a suitable jack stand before removing the transmission from the engine.




27. 5.0L and 5.7L Gasoline Engine: Remove the studs and bolts securing the transmission to the engine.




28. 4.3L Gasoline Engine: Remove the studs and bolts securing the transmission to the engine.
29. Pull the transmission straight back from the engine.
30. Lower the transmission using the transmission jack.
31. Flush the transmission oil cooler and the pipes whenever you remove the transmission for overhaul, or replacement of the torque converter, the pump, or the transmission case. Refer to Transmission Fluid Cooler Flushing .
32. Clean the transmission case using a solvent dampened cloth. Do not allow solvent to enter the transmission.
33. Air dry the transmission.
34. Clean all hardware and the flywheel cover using solvent. Air dry all the parts.
35. Inspect all the components for wear and damage.
36. Inspect all the seals and the fittings for signs of wear.
37. Inspect the torque converter for stripped or broken weld nuts.
38. Inspect the transmission case for cracks.

sorry but your stuck with the 4l60e if you want it to be right. as for using the bravada transmission thats fine you just have to use your transfer case. your transfer case uses a switch on the dash and an electric motor on the transfer case. the bravada uses a series of sensors on the front and rear axle that sense wheel slippage and send a signal to the electric motor on the transfer case causing it to lock in four wheel drive. when the sensors dont sense wheel slippage any more the system returns to two wheel drive. that,s why they call it smart track. just unbolt your transfer case from your transmission and bolt it to the bravada transmission and install it. p.s- dont forget to at least change the front pump converter seal. for 4 or 5 bucks it,s cheap insurance against a major leak and i dont think you want to pull that transmission out again and yes i saw that happen to many times. good luck.-G.J.M

Does it sound like a loud winding sound coming from the front right side? I have a 2001 Jimmy and the 4wd tries to engage when driving up steep hills and going at highway speeds. The actuator vacuum switch engaged when the transfer case vacuum switch sends the vacuumed air to the actuator. What is happening is their is either a leak in the vacuum lines, a faulty actuator switch, or a faulty transfer case vacuum switch. When the jimmy has enough air pulling in, the extra vacuum is trying to push the actuator switch in when it is not supposed to. It is a much cheaper fix than a transmission. GMC should have recalled the whole 4wd system on any of the S10's, the JImmy's, and Blazers.