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Causes & Solutions: 4wd Transfer Case Position Sensor Selector Switch Failure

4wd Transfer Case Position Sensor Selector Switch Failure

Thanks to a vehicle’s 4×4 drivetrain you can enjoy better traction and stability especially when driving offroad and during heavy snow and rain. The drivetrain transmits torque to all 4 of the vehicle’s wheels. Then there is what we call the transfer case which allows you to switch from two-wheel to four-wheel drive. The transfer case is what sets 4WD vehicles from 2WD. It consists of several parts which work together to deliver engine power to the front and/or rear differentials. One of its important parts is the 4WD transfer case position sensor switch and when this part fails to work you will have a problem transferring shift in your 4WD. 

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Before we look into what happens when a transfer case switch goes bad and what to do about it, let’s first discuss what a 4WD transfer case position sensor switch does. 

What does a transfer case switch do?

This switch allows you to easily engage and disengage the vehicle’s four-wheel drive capability. In older vehicles, you have to get off the vehicle and lock the wheel hubs manually to enable 4WD, but these days vehicles now come with a transfer case switch allowing you to conveniently electrically shift from two-wheel to four-wheel and vice versa.


Transfer cases that are mechanically operated also have this switch part though it is not used to control the drivetrain. What it only does is illuminate the light on the dashboard to let you know if the four-wheel drive capability of your vehicle is engaged or not.


Like the rest of your car parts, the transfer case switch will eventually wear down over time, more quickly if you always use it for driving offroad. Aside from normal wear and tear, there are also other things that could cause this part to stop working before its expected service life. For example, it can get contaminated with dirt and debris interrupting electricity flow or causing loose electrical connections. Another common cause of a transfer case failure is corrosion. 

How do I know if my transfer case is bad?

Ideally, the transfer case should last the lifespan of your vehicle. Unfortunately, it doesn’t always happen. Here are some of the most common indications of a failing transfer case:


Problems with Gear Shifting

One common sign of a bad transfer case is when you are having trouble shifting between gears. The reason for gear shifting issues can be a minor one like a low fluid level or damaged linkage, but oftentimes it means an internal transfer case failure. But make sure to refer to your car owner’s manual and follow directions in operating your transfer case before assuming that there is a problem. Most of the time, before shifting into four-low, your vehicle should be stopped and the transmission must be in neutral. If not, grinding noise will be produced when shifting gears. 


Having a Hard Time Staying in 4WD

Another typical issue is when a transfer case pops out of 4WD. It can be due to external factors like a problem with the driveshaft or differential, or it might be because of an issue inside the transfer case. 


4WD Fails to Engage or Disengage

This issue can be caused by several reasons. A faulty shift mechanism on the mechanism could be the reason you cannot engage or disengage. It could also be due to an electrical fault in the control system, or internal problems in the transfer case. 


Puddle Buildup Right Under the Location of the Transfer Case

The only reason a greasy puddle is forming under your car is a leak somewhere and that could be a leak in the transfer case. You can confirm this by jacking up your vehicle and visually checking it. You can locate it at the rear end part of the transmission or transaxle assembly.


Odd Grinding or Humming Noises

Strange noises coming from your car should never be ignored. This is one of the most common signs you have an issue in your car, but this could mean several things. It could be a minor issue or a major one. But if you hear this grinding noise that changes with car speed, the problem is probably from the transfer case due to low fluid level or a mechanical issue like a loose chain, damaged gears or bad bearings. 


4WD Warning Light is On

There are vehicles that come with a service four-wheel drive message or something similar to it on the dashboard that lets you know when there’s an issue in the system. Other cars will simply have the 4WD light on continuously to tell you there’s a problem which could be a failing transfer case. 


What causes a transfer case switch to go bad?

The symptoms above can also be caused when the 4WD transfer case position sensor switch gets stuck in one particular position and is unable to shift. It is not unusual for truck owners to face this problem. Here are common reasons a transfer switch goes bad:


Mismatched Tires and Inflation

All your tires should be within a quarter of overall circumference. A mismatch in the tires can result in viscous coupling in the tires that would cause differentials to malfunction. Also, the tire pressure should be correct too. A little bit of deflation in the tire can cause resistance when shifting from 2wd to 4wd, and vice-versa. This problem is one of the easiest to identify.


Dirt and Water

When water and dirt get into the system, it can mean trouble to your transfer case switch particularly on the wiring or the encoder motor. These external elements may cause corrosion and rusting on the harness which will prompt the computer to detect inaccurate resistance and do unnecessary shifts. To avoid dirt and water from damaging your system, drive smoothly through any terrain and be sure that dirt and water do not build up in big chunks. Once you are back from a trip, give your truck a good servicing and wash it too.  


Bad Shaft Seal

Your transfer case’s output shaft seal is responsible for keeping it safe from hydraulic fluid leaks. When they fail to work as it should be, leaks are likely to happen. Such leaks can cause problems in gear shifting and related functions to shifting over to 4wd. When your transfer case problem is due to hydraulic fluid leak, it requires the attention of a professional mechanic. Only automotive experts can really tell you what went wrong and repair it accordingly.


Transfer Case Switch Replacement

A failing 4wd transfer case position sensor selector switch is one of the most common reasons behind transfer case failure in four-wheel drives. A mechanic can diagnose the issue in several ways. One of the first things your mechanic will check is the switch’s voltage input and output. They may also check the wirings and connectors for indications of corrosion and loose connections. 


You can still drive with a bad transfer case but the transmission will most likely not work properly or as it should be, making the ride hard to control. This is particularly difficult when you need to change gears or engage the 4wd. On top of that, your vehicle is at risk of getting more or bigger issues on the transfer case and drivetrain which could lead to expensive repairs. This is why it is highly recommended to have a failing transfer case switch replaced before driving your vehicle again. The good news is, replacing a transfer case won’t cost a lot of time and money.


How much does it cost to replace a transfer case switch?

How much you’ll spend on replacing a transfer case switch will depend on the brand of the product you’re getting, your vehicle’s model, year and make. OE replacement transfer case switches’ cost can range from $20 to $80. These are sold individually and are available in various terminal types and connector quantities. You also don’t have to worry about installation since there are transfer case switches that come in a direct-fit design to make installation quick and easy. 


Before buying the replacement, you should make sure that the transfer case switch you will buy is compatible with your vehicle. You can refer to your car owner’s manual or the car manufacturer’s website to be sure you have the right specifications of the transfer case components.

Guide on Replacing a Broken Transfer Case Switch 


The transfer case is controlled by the 4wd transfer case position sensor selector switch, and if the switch fails to function you are unable to shift your car into four-wheel drive. A damaged transfer case switch might cause the service 4wd message in your dashboard to illuminate, but if it’s difficult to get the transmission to shift to 4wd then it is necessary for you to have your transfer case and its switch inspected and changed if needed. 


Replacing a transfer case switch is moderately difficult. You will need a socket set, jack stand and jack. Follow the following steps:


  1. Lift the rear end of your vehicle using the jack. Slide the jack stands below the rear frame and lower your vehicle in place.
  2. Open the hood of your vehicle and use a socket wrench to disconnect the negative battery cable.
  3. Locate the transfer box at the rear end of your vehicle. You can also check the vehicle’s user manual to find out where the transfer box is placed.
  4. Detach the electrical connections, vacuum lines and shift lever that connect to the transfer case.
  5. Remove the bolts that keep the transfer box in place carefully. You should be able to access the switch once the bolts are taken off.
  6. Unplug the wiring harness from the switch’s back. Once the harness is disconnected, pull the switch out carefully.
  7. Put the new switch on the transfex box and reattach the harness.
  8. Change and tighten the bolts on the transfex box. Reconnect the electrical connection, the battery cable, vacuum lines and shift lever.
  9. Lower and take off the jack stands from the vehicle’s rear and start your engine. Now you can check if the 4wd transfer case position case switch is working as it should be.


How do I get my 4 wheel drive unstuck?

Becoming stuck in four-wheel mode because of lack of use or improper lubrication is a common issue with four-wheel drive vehicles. Usually, it is not a major issue. Switching to two-wheel drive when transitioning to a hard surface is important since driving in 4wd mode on the highway decreases fuel economy and can cause damage. Here’s how you can unstuck your 4wd:

  1. If you have manual hubs, check them if they are in free mode.
  2. Set your vehicle into 4wd mode.
  3. Drive forward for half a kilometer.
  4. Stop your vehicle and shift from 4wd to 2wd.
  5. Put your vehicle in reverse and drive backwards for 15 feet. Then drive your vehicle forward slowly to let the loosened shims to disengage.

When should I change transfer case fluid?


Transfer case fluid can be synthetic or traditional gear oil. However, certain vehicles need particular types of transfer case fluids. Transfer case fluid is important since it keeps gears cool and turning smoothly. Like other automotive fluids, it gets contaminated over time. A carbon build up from cooling hot drivetrain parts can contaminate it which then affects the performance of the vehicle. The vehicle may produce whining noise or shudder when turning. When the transfer case fluid runs low or gets contaminated, it can cause damage to the differential. To prevent this from happening, you should change your transfer case fluid periodically. Normally, it should be changed every 30,000 miles especially if you often use your vehicle for towing or having it on 4wd mode often.But you can wait until 70,000 miles before changing the fluid if you do not often tow or use 4wd frequently. Regularly changing your transfer case fluid in recommended intervals will lessen the chance of any drivability issue. Transfer case fluid replacement is cheaper and quicker to do than replacing a differential



A transfer case plays an important role in your four-wheel drive vehicle. To make sure it is working as it should be, any problems like an issue with your 4wd transfer case position selection switch should be addressed right away. Also, it is important for you to regularly change your transfer case fluid to keep your transfer case system in good condition.  

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