Service 4wd, Transfercase Shows Neutral.
Service 4wd, the transfer case shifter showing the wrong range or the buttons are not illuminated. This is one of a few issues that plagues many GM, and Chevy vehicles.
This fix is for the 2003-2007 old body style trucks, Tahoe, Suburbans and Avalanches. It is specific to the New Process transfer case with a model of Np246. You can confirm with the RPO code in the glove box. This is the white sticker with all the 3 character codes. The code for this transfer case is NP8.
So now that we have identified the transfer case involved lets talk for a moment about the cause. In the shifter on the side of the transfer case is a 3 wire sensor called a potentiometer. This sensor has a coating on the surface that has a resistance that increases by the length between contacts. On the other half of the sensor is a pair of small spring steel fingers that slide on the surface. After enough time those fingers wear through the surface and then the reading or resistance changes. The result is the shifter showing neutral when you are driving along, the service 4wd and likely the lights being out.
OK, so far this fits your issue. The next thing to check is that the you need to check is the transfer case fluid. This takes an 18mm socket or wrench. If the fluid is blue or green, and not black and very smelly, then things are good. If the fluid is black, then the clutch pack in the transfer case has worn out and that is why the sensor is out of range.
OK, so we have determined that we need the sensor. So here are the part numbers. The sensor is 88962315, the case gasket is 12374990 , and finally you will need a new clamp for the drive shaft boot on the front, 26064275.
You will need a small number of tools.
- Jack stands and a jack or a set of car ramps to get under the vehicle.
- An 11mm or 7/16 wrench.
- A 15mm socket or wrench
- A flat blade screw driver.
- 2 torx screw drivers, T15 and T20.
Start with your vehicle in 2wd the get under your vehicle. Be sure to have it safely supported so you will survive to brag about your repair. Take the skid plate off the cross member that holds the transmission. There are 4 15mm bolts.
Next find the end of the clamp and use your blade screwdriver to pry it up and release it so you can remove the drive shaft.
Remove the 4 bolts that hold the front drive shaft to the front yoke. These are the 11mm or 7/16. Use the screw driver or a pry bar or crow bar to pop that loose. There is enough room then to slide the drive shaft out. Set it to the side so the splines don’t get dirty.
Next find the electrical connector. It is usually attached to a small flate bracket above the front drive shaft. Pry that loose from the flat bracket. The slide the grey retainer back and squeeze the tab to separate the connector.
Remove the 3 15mm bolts that hold the shift assembly to the transfer case.
Set the assembly on a work surface. Set the gasket/spacer to the side.
Remove only 4 screws. 2 on the outside of the long back tube, and the 2 on the other side of the case. Gently pry the case apart.
Lift the cover off and set it aside. Mark the position of the gear before lifting it out.
Lift the gear out and flip it over. Disconnect the connector
Slide the black sensor off the gear.
Install the new sensor, and hook the connector up making sure the connector is lined up correctly
Make sure the 2 small washers are where they need to be. Often the big one will stay on the large gear and the smaller one will stay on the case.
Put them over the gears.
Make sure they are set down completely over the shaft of each gear, not sitting like the picture above.
Next install the new seal for the housing and install the housing cover. Install the 4 screws and install the black case seal to the unit.
Install this back into the truck, connect the connector, install the drive shaft, the clamp and skid plate.