Silverado pickup trucks to be born for a life of difficult work. The option of 4WD typically means adding much more components, switches, motors, and controllers come the vehicle, do a hard-working truck work even harder. Yet if the 4WD starts to act up, then what? This write-up includes the procedures you can take to track down the problem.

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

In the negative old days, putting your spartan-finished, harsh-riding auto into 4WD compelled that girlfriend stop, acquire out, and also manually lock each of the grimy prior wheel hubs. Climate get back in, clean your now-filthy hands v a moist towelette, shift the brand-new Process (OEM transfer case-maker for almost every vehicle—now brand-new Venture) floor-mounted lever right into 4-high or 4-low—which often forced jockeying your car a bit forward or behind so the gears might mesh,—and finally driving away. If her 4WD device acted up (like one or both hubs wouldn"t lock or the transfer situation lever refuse to communicate or disengage), you automatically knew what to be wrong.

But those work are lengthy gone. Today, every that"s forced to walk four-wheeling is slowing your Silverado down listed below 70 mph, and also then turning a switch from 2-High come 4-High. Then, again, you could just leave it in “Auto” during questionable steering conditions. And also compared to the previously-mentioned “bad old days,” how amazing is it with “Auto” to have the PCM, using traction, stability, wheel speed, and also other road condition inputs decide whether her truck have to be in 4WD or 2WD because that you?

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

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

Step 1 – examine the transfer case selector switch

It is situated on the left next of the dashboard. Just how the transfer situation selector switch behaves can be your very first clue the your 4WD system has actually a problem, and likewise what could be the feasible cause.

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

If your transfer situation selector switch:

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

In the occasion that one of two people of the very first two items listed above room what you’re experiencing, instead of the selector switch is in order. But prior to you carry out that, plenty of have found that the soil wires attached come the TCCM can provide an poor or intermittent ground. This ground wires space attached to the framework under the front of the driver’s door. Unbolt these wires, clean their contact area to bare metal as well as the bolt threads, and also reattach the wires come the structure (a 5-minute job).

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Figure 2. Transfer case selector move replacement.

If the soil wires space okay, change the transfer instance selector switch. To execute this, eliminate the instrument dashboard knee bolster, and also then usage an proper tool to boring the tabs to eliminate the switch 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 instance control module (TCCM).

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Step 2 – inspect the dashboard warning irradiate (TCCM)

The dashboard DIC warning light (indicating the should “service 4WD”) will rotate on. This can take place if the transfer situation control module (TCCM) senses a communication failure in between it and also the powertrain regulate module (PCM). If this occurs, the TCCM turns on the warning light in the IP. If the light turns on ~ the car has been pushed awhile with no issues, the TCCM is suspect.

Be aware that there have actually been problems and a recall worrying the TCCM’s controller software, bring about the transfer instance to unexpectedly switch to “Neutral” as soon as parked or moving. The equipment for this is having the TCCM re-flashed (overwritten with brand-new firmware). Inspect to watch if your auto was component of this recall, and also if that was, have actually the dealer re-flash the TCCM.

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Figure 3. Organization 4WD tool panel message (alternate format on the right).

Controller interaction issues in between such materials as the former axle actuator and also transfer case change motor will commonly be indicated by the the transfer instance selector switch (see action 1).

To execute a quick inspect to watch if the PCM is communicating properly with the TCCM, try the following:

Turn the ignition on, however keep the engine off.Put the selector move through all of its modes, while both the town hall the behavior of the dashboard warning light area and also the selector switch lights, and also listen carefully for component activation noises from under the former of the vehicle.

Running with the selector move choices, beginning from the “normal” an option of “2-Hi,” should attain the following:

In "2-Hi," the front axle is no engaged and the transfer instance only sends power come the behind wheels.Turning it come “Auto” engages the prior driveshaft via the former axle actuator (no much more locking wheel hubs!), and keeps the front axle involved to make instantly switching to and also from 2WD and also 4WD much faster (“Auto” can’t select “4-Low).By turning it to “4-Hi” (at much less than 70 mph only) with the prior axle actuator currently engaged native the previous place (“Auto”), the transfer instance is shifted by the carry case shift motor from 2WD, past Neutral (as provided previously the transfer case has its own Neutral mode) come “4-Hi.”Turning it come “4-Low” (at speeds much less than 3 mph or stopped, and also with the infection in Neutral, no Park, with the parking brake on) through the prior axle encoder tho engaged, the transfer instance actuator engine is shifted from 4-Hi to 4-Low.

If the most apparent culprit watch to it is in the transfer situation control module, climate you will find it behind the dash top top the drivers" side. But, as stated previously, if you haven’t already done so, first check the ground wire relations going come the framework under the former of the driver’s door. Ensure that they space clean and also tight, and also not bring about a floor fault. If they’re not the problem, you’ll have to replace the TCCM.

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Figure 4. Transfer situation control module replacement.

If friend unplug and also replace her TCCM through a compatible supplied one, it might be set up because that a different final drive ratio. It can work, but with the automatically Transfer case option, you will need to keep your truck out of the “Auto” choice until girlfriend have had actually your replacement TCCM re-flashed in ~ a dealership with firmware for her vehicle’s drivetrain configuration.

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Step 3 – check the front axle actuator

Finding the end if the front axle actuator is the culprit is not daunting to test.

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Figure 5. Prior axle actuator replacement.

With the vehicle up ~ above jacks, the ignition on with the motor off, and “4-Hi” selected, the front differential must be involved to the carry case, and also the former tires need to not be able to spin without moving the front driveshaft. If they can spin, very likely you have to replace the prior axle actuator.

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Figure 6. Prior axle actuator mounted in a prior axle.

To eliminate the front axle actuator, unplug the wiring harness and remove the actuator"s screws from the prior differential casing. As soon as replacing it, be certain to usage the suitable sealer and tighten it to the suitable torque.

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

Step 4 – examine the transfer case transition motor

The move case change motor, periodically referred to as the “shift actuator” or “shift encoder,” is attached straight to the carry case. It might be the culprit if you’re not able to select a different drive mode with the transfer situation selector switch.

When the drive mode is switched from “2-Hi” come “4-Hi,” the actuator motor transforms a column in the transfer situation to one of four feasible settings: “2-Hi,” Neutral, “4-Hi,” and also “4-Low.” If friend don’t hear this transition happening (the selection of “4-Low” gift the loudest) or hear that trying to do the change but failing, opportunities are girlfriend will should replace the transport case transition motor.

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Figure 7. Deliver case transition motor replacement.

Note the you will need to remove the prior drive obelisk to replace the encoder motor. Three bolts organize the encoder engine on, and also if the old encoder’s gasket is in great condition, it deserve to be reused.

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Materials NeededLong and also short handle socket set 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 transport case change actuator motor is much more likely to need replacement 보다 the transfer situation itself, the must replace the transfer instance does wise. A proviso to troubles with it would be if it has actually been make a strange grind noise as soon as engaged, or was doing so prior to it stopped working altogether.

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Figure 8. Transfer case replacement.

Perform the following:

Drain the oil the end of the transport case.Remove the skid plate below the deliver ace.Remove the prior drive pillar completely.Prop the infection up indigenous underneath.Detach the behind drive obelisk at the rear differential.Remove the crossmember listed below the transmission, and also nuts it is registered it to the 2 transmission mount bracket bolts.Remove the transmission mount bracket from the bottom of the transmission.Lower the transmission until its rear rests top top the crossmember beneath it.Unplug all of the electric connections, and remove the exploit tangs as well as vent tube.Remove the six nuts hold the transfer situation to the transmission v a pan beneath to record the fluid.Remove the transfer instance (easier v two people).

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To install the brand-new transfer case, turning back the procedure.