Silverado pickup trucks were born for a life of tough work. The alternative of 4WD typically way adding much more components, switches, motors, and also controllers to the vehicle, do a hard-working van work even harder. But if the 4WD starts to act up, climate what? This post includes the actions you have the right to take come track down the problem.

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This article uses to the Chevrolet Sillverado GMT900 (2007-2013).

In the poor old days, placing your spartan-finished, harsh-riding automobile into 4WD compelled that you stop, obtain out, and also manually lock each of the grimy prior wheel hubs. Then get back in, clean her now-filthy hands through a moist towelette, transition the brand-new Process (OEM move case-maker for virtually every vehicle—now brand-new Venture) floor-mounted lever right into 4-high or 4-low—which often required jockeying your car a little forward or backward so the gears could mesh,—and finally driving away. If your 4WD device acted increase (like one or both hubs wouldn"t lock or the transfer instance lever refused to interact or disengage), you immediately knew what to be wrong.

But those days are long gone. Today, every that"s compelled to walk four-wheeling is slowing her Silverado down listed below 70 mph, and also then transforming a switch from 2-High to 4-High. Then, again, you might just leaving it in “Auto” throughout questionable steering conditions. And also compared to the previously-mentioned “bad old days,” how amazing is it through “Auto” to have actually the PCM, making use of traction, stability, wheel speed, and also other road condition inputs decide whether her truck must be in 4WD or 2WD because that you?

In this article, investigating possible 4WD problems will be damaged down into five steps:


Material NeededFlat-blade driver or plastic trim removal tool for un-clipping dashboard tabs

Step 1 – examine the transfer situation selector switch

It is located on the left side of the dashboard. Exactly how the transfer case selector switch behaves can be your an initial clue that your 4WD system has a problem, and also what could be the possible cause.

Figure 1. Transfer instance selector move (on the right).

If your transfer instance selector switch:

Doesn"t light up in ~ all once you begin your vehicle, then your transfer instance selector switch is the suspect.Won’t switch right into the drive setting you’ve selected (that is, the place indicator won’t continue to be lit in that selection), climate again the selector move is the suspect.Lights up when you start your automobile but then goes off by itself, then your Transfer instance Control Module (TCCM) is the suspect (a “Service 4WD” dashboard warning light may likewise come on).Switches into 4WD simply fine yet your car isn’t actually sending power to the former wheels, then her front axle actuator is the suspect.Blinks through nothing continue (drivetrain-wise), then her transfer case actuator engine (the motor the shifts the transfer case mode selections) or the transfer situation itself is the suspect.

In the event that either of the very first two items listed above are what you’re experiencing, replacing the selector switch is in order. But prior to you carry out that, numerous have discovered that the ground wires attached to the TCCM can give an poor or intermittent ground. This ground wires space attached come the frame under the prior of the driver’s door. Unbolt this wires, clean their contact area to ceiling metal as well as the bolt threads, and reattach the wires come the framework (a 5-minute job).

Figure 2. Transfer case selector switch replacement.

If the soil wires space okay, replace the transfer instance selector switch. To carry out this, eliminate the instrument panel knee bolster, and then usage an appropriate tool to boring the tabs to eliminate the move assembly from the bezel. Remove the plugs indigenous the back of the switch and plug in the brand-new switch.

If this doesn’t correct the problem, then the following suspect is the transfer case control module (TCCM).


Step 2 – inspect the dashboard warning light (TCCM)

The dashboard DIC warning light (indicating the should “service 4WD”) will revolve on. This can take place if the transfer situation control module (TCCM) senses a interaction failure between it and also the powertrain manage module (PCM). If this occurs, the TCCM turns on the warning irradiate in the IP. If the light transforms on after ~ the automobile has been propelled awhile v no issues, the TCCM is suspect.

Be aware that there have actually been problems and also a recall worrying the TCCM’s controller software, resulting in the transfer instance to suddenly switch come “Neutral” once parked or moving. The systems for this is having actually the TCCM re-flashed (overwritten with brand-new firmware). Inspect to see if your vehicle was part of this recall, and also if it was, have the dealer re-flash the TCCM.

Figure 3. Organization 4WD tool panel blog post (alternate layout on the right).

Controller communication issues between such components as the front axle actuator and transfer case transition motor will typically be suggested by the the transfer instance selector move (see step 1).

To execute a quick check to check out if the PCM is interacting properly with the TCCM, try the following:

Turn the ignition on, yet keep the engine off.Put the selector switch through all of its modes, when both the town hall the habits of the dashboard warning irradiate area and also the selector move lights, and also listen closely for component activation noises native under the prior of the vehicle.

Running with the selector switch choices, starting from the “normal” an option of “2-Hi,” should accomplish the following:

In "2-Hi," the front axle is no engaged and also the transfer case only sends out power to the rear wheels.Turning it to “Auto” engages the former driveshaft via the front axle actuator (no an ext locking wheel hubs!), and keeps the prior axle involved to make instantly switching to and also from 2WD as well as 4WD quicker (“Auto” can’t pick “4-Low).By transforming it come “4-Hi” (at much less than 70 mph only) v the front axle actuator currently engaged native the previous place (“Auto”), the transfer situation is shifted by the transport case change motor native 2WD, past Neutral (as listed previously the transfer case has its own Neutral mode) come “4-Hi.”Turning it to “4-Low” (at speeds less than 3 mph or stopped, and with the infection in Neutral, not Park, v the parking brake on) with the former axle encoder quiet engaged, the transfer situation actuator engine is shifted from 4-Hi to 4-Low.

If the most evident culprit look at to it is in the transfer case control module, then you will discover it behind the dash on the drivers" side. But, as discussed previously, if friend haven’t already done so, first check the floor wire relations going to the frame under the former of the driver’s door. Ensure that they space clean and tight, and not resulting in a ground fault. If they’re no the problem, you’ll must replace the TCCM.

Figure 4. Transfer instance control module replacement.

If you unplug and replace your TCCM v a compatible used one, it may be set up because that a different final journey ratio. It have the right to work, however with the automatic Transfer situation option, you will have to keep her truck out of the “Auto” selection until friend have had actually your instead of TCCM re-flashed in ~ a dealership with firmware for your vehicle’s drivetrain configuration.


Step 3 – inspect the prior axle actuator

Finding the end if the prior axle actuator is the culprit is not difficult to test.

Figure 5. Former axle actuator replacement.

With the vehicle up ~ above jacks, the ignition on through the motor off, and “4-Hi” selected, the prior differential need to be involved to the move case, and also the front tires should not be able to spin without relocating the prior driveshaft. If they have the right to spin, really likely you need to replace the prior axle actuator.

Figure 6. Former axle actuator installed in a prior axle.

To eliminate the prior axle actuator, unplug the wiring harness and remove the actuator"s screws indigenous the front differential casing. Once replacing it, be certain to use the proper sealer and tighten it come the appropriate torque.


Materials NeededSocket set with metric and/or star (Torx) sockets and also extensionsSmall pry bar or big screwdriver

Step 4 – check the deliver case change motor

The transfer case transition motor, occasionally referred to together the “shift actuator” or “shift encoder,” is attached directly to the transport case. It might be the culprit if you’re no able to select a different drive mode with the transfer case selector switch.

When the drive setting is switched from “2-Hi” to “4-Hi,” the actuator motor turns a obelisk in the transfer situation to one of four possible settings: “2-Hi,” Neutral, “4-Hi,” and “4-Low.” If girlfriend don’t listen this change happening (the selection of “4-Low” being the loudest) or hear it trying to make the change but failing, possibilities are friend will should replace the move case change motor.

Figure 7. Move case shift motor replacement.

Note that you will need to remove the front drive shaft to change the encoder motor. 3 bolts host the encoder engine on, and also if the old encoder’s gasket is in an excellent condition, it deserve to be reused.


Materials NeededLong and also short handle socket collection with metric and/or star (Torx) sockets and extensionsBox wrench setRatchet wrench setSmall pry bar or big screwdriver

Step 5 – inspect the transfer case (noisy)

Although the carry case transition actuator motor is much an ext likely to call for replacement 보다 the transfer case itself, the must replace the transfer case does wise. A clue to problems with it would certainly be if it has actually been making a strange grind noise once engaged, or to be doing so prior to it quit working altogether.

Figure 8. Transfer case replacement.

Perform the following:

Drain the oil out of the move case.Remove the skid plate below the transport ace.Remove the former drive column completely.Prop the transmission up native underneath.Detach the rear drive shaft at the rear differential.Remove the crossmember below the transmission, and also nuts it is registered it to the two transmission mountain bracket bolts.Remove the infection mount bracket native the bottom that the transmission.Lower the transmission until its behind rests on the crossmember in ~ it.Unplug every one of the electrical connections, and also remove the exploit tangs and also vent tube.Remove the 6 nuts hold the transfer case to the transmission v a pan in ~ to record the fluid.Remove the transfer case (easier v two people).

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To download the new transfer case, turning back the procedure.