Replacing the transfer case

It depends on what is wrong , is the 4x4 light flashing ? Are you aware of the complexity of the 4x4 system ? Has a electronic control module , has the ability to set an store DTC'S - diagnostic trouble codes !
Transfer Case The four wheel drive system is an electronic shift 4X4 system that allows the operator to choose between three different modes. The operator can switch 4X4 HIGH modes at any speed. To engage or disengage 4X4 LOW the vehicle speed must be less than 5 kph (3 mph), the brake depressed, and the transmission must be in NEUTRAL.
The shift motor sense plate, an integral part of the electronic shift motor, informs the generic electronic module (GEM) of the transfer case shift motor and contact plates A, B, C and D position.
The digital transmission range (TR) sensor is located on the LH side of the transmission, and informs the GEM when the transmission is in the NEUTRAL position.
The electronic shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4X4 HIGH, 4X4 LOW and 2WD range positions.
When the GEM verifies the completion of the transfer case shift from 2WD to 4X4 HIGH (reading the contact plate positions), the GEM will then energize both pulse vacuum hublock (PVH) solenoids (supplying ground for 45 seconds). The PVH solenoid will allow a HIGH flow of intake manifold vacuum to the "wheel end hublocks", engaging the wheel end hubs to the front differential and transfer case to achieve four wheel drive.
Here are just a few DTC'S the system can set an store in the module !
P1804 4WD High Indicator Circuit Failure GEM GO to Pinpoint Test C . P1806 4WD High Indicator Short to Battery GEM GO to Pinpoint Test C . P1808 4WD Low Indicator Circuit Failure GEM GO to Pinpoint Test C . P1810 4WD Low Indicator Short to Power GEM GO to Pinpoint Test C . P1812 4WD Mode Select Switch Circuit Failure GEM GO to Pinpoint Test A . P1815 4WD Mode Select Switch Circuit Short to Ground GEM GO to Pinpoint Test A . P1820 Transfer Case CW Shift Relay Circuit - Failure GEM GO to Pinpoint Test A . P1822 Transfer Case CW Shift Relay Coil Short to Power GEM GO to Pinpoint Test A . P1824 4WD Electric Clutch Relay Circuit Failure GEM GO to Pinpoint Test A . P1826 4WD Low Clutch Relay Short to Power GEM GO to Pinpoint Test A . P1828 Transfer Case CCW Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test A . P1830 Transfer Case CCW Shift Relay Coil Short to Battery GEM GO to Pinpoint Test A . P1838 Transfer Case Shift Motor Circuit Failure GEM GO to Pinpoint Test A . P1846 Transfer Case CONTACT PLATE "A" Circuit Failure GEM GO to Pinpoint Test A . Now are you sure you really want to mess with this ? You would need a factory diagnostic scan tool to check this out before you start replacing parts !
Here

The electronic module (located behind the glove compartment) controls the operation of the transfer case in response to inputs from the electric shift motor, 4x4 mode switch, CPP switch, BPP switch, DTR sensor, throttle position output from the PCM, front and rear OSS sensors, and the VSS. Do you know what DTC'S Are ? Diagnostic trouble codes !

P1804 4WD High Indicator Circuit Failure GEM GO to Pinpoint Test C . P1806 4WD High Indicator Short to Battery GEM GO to Pinpoint Test C . P1808 4WD Low Indicator Circuit Failure GEM GO to Pinpoint Test C . P1810 4WD Low Indicator Short Circuit to Battery GEM GO to Pinpoint Test C . P1812 4WD Mode Select Circuit Failure GEM GO to Symptom Chart. P1815 4WD Mode Select Short Circuit to Ground GEM GO to Symptom Chart. P1820 Transfer Case CW Shift Relay Coil Circuit Open or Short to Ground GEM GO to Pinpoint Test B . P1822 Transfer Case CW Shift Relay Coil Short to Battery GEM GO to Pinpoint Test B . P1824 4WD Electric Clutch Relay Circuit Failure GEM GO to Pinpoint Test A . P1826 4WD Electric Clutch Relay Short to Battery GEM GO to Pinpoint Test A . P1828 Transfer Case CCW Shift Relay Circuit Failure GEM GO to Pinpoint Test B . P1830 Transfer Case CCW Shift Relay Coil Short to Battery GEM GO to Pinpoint Test B . P1836 Transfer Case Front Shaft Speed Sensor Circuit Failure GEM GO to Symptom Chart. P1837 Transfer Case Rear Shaft Speed Sensor Circuit Failure GEM GO to Symptom Chart. P1838 Transfer Case Shift Motor Circuit Failure GEM GO to Pinpoint Test B . P1846 Transfer Case CONTACT PLATE "A" Circuit Failure GEM GO to Pinpoint Test B . P1850 Transfer Case CONTACT PLATE "B" Circuit Failure GEM GO to Pinpoint Test B .

P1854 Transfer Case CONTACT PLATE "C" Circuit Failure (GEM Only) GEM GO to Pinpoint Test B . P1858 Transfer Case CONTACT PLATE "D" Circuit Failure (GEM Only) GEM GO to Pinpoint Test B . P1866 Transfer Case Maintenance Required (GEM Only) (4-wheel drive operation can be restored by clearing the DTC and cycling the ignition.) GEM GO to Pinpoint Test B . P1867 Transfer Case Contact Plate General Circuit Failure (GEM Only) GEM GO to Pinpoint Test B . P1874 Automatic Hall Effect Sensor Power Circuit Failure GEM GO to Symptom Chart. P1875 Automatic Hall Effect Sensor Power Circuit Short to Battery (GEM Only) GEM GO to Symptom Chart. P1891 Transfer Case Contact Plate Ground Return Open Circuit GEM GO to Pinpoint Test B Your best bet , take it to a qualified repair shop

I have a 1999 Dodge Durango and I have replaced the front and rear differental twice because of a transfer case problem. I would use the part time 4W D and then I would shift out of it and back to regular drive as soon as I got off the ice. The light would go out on the dash letting me know I was no longer in 4WD, so I thought. Even though It said I was out of 4WD I was not and I burned up all that stuff again, this didnt happen ever time only occasionaly so now what we have to do and its an cheap easy fix. Just put truck in revere for a couple hundred feet than go forward make a hard sharp turn and you will know for sure if you are out of 4WD.

The most common problem with these would be the transfer case 4x4 actuator motor or also called transfer case selector motor, testing would be a good thing to do before replacing it.

This is going to be in the synchros in the T-case. The most economical way is to either have the unit rebuilt or replaced used. If you need any other info, let me know.

If 4wd Tahoe, it is the CV joint going out or is out, replace part about 250 bucks, very common in 4wd Tahoe

If your luck it's going to be a $15.00 vacuum switch on the transfer case that takes about 15 min to replace, if it's the electronic solenoid to the transfer case then it's going to be cost a little more and take a little longer. If your try switching from 4WD to 2WD and hear the solenoid working by hearing the cluck's when it engages and disengage then it's going to be the vacuum switch on top of the transfer case on the drivers side. Auto Zone Sell's them for $15.00 and they will have the step by step instructions to replacing the switch. They will also have the transfer case solenoid  too, if you don't hear the solenoid. Check the fuses, the fuse may have gone bad. Good luck and hope this helps.

Sounds like the transfer case is not fully engaging itself. you will have to check this out. This will only cause more damage if left alone. make sure the wires are connected and tight. if the wires are OK, the internals are likely to be malfunctioning. replacing or repairing the transfer case will fix this.

It seems like no one else hear at FixYa is responding yet to both your requests about clunking in 4wd.
I see two requests....in the first a 2000 blazer from Gloeckz
there is a rapid clunking in 4wd!
In the second it clunks hard going in then won't drive!
This is rayenc11s' 98 Jimmy 4WD clunk I'm no trans specialist and not familiar with repairing or troubleshooting serious 4wd problems but it sounds like this may be a problem in the transfer case.

Since no one seems to be helping you but me I'd suggest you go to a transmission shop and ask them if this is a common problem that may lead to a bad transfer case if not corrected!

Make sure you have the proper fluid in your transmission case, transfer case and differential case first or have a quick oil change place check it for you!

Hope this is helpful.

Good Luck!
jackiaria

I have the same problem the switch is on the transfer case! what your talking about is your vehicale information center. the stupid thing sucks I also replaced it but it only comes on some times now. dont know!