2003 gmc envoy 4x4 problems. 4200 vortec engine. my front diff doesnt seem to be working

check transfer fluid it might be low

Does it have half a tank or is it empty ? Fuel gauge wrong .

Neither work? replace the turn signal switch.

Does the driveshaft for the front wheels turn when in 4wd? The actuater might work but the diff lock for the front wheels might have broken. If the front driveshaft does not turn when in 4wd, the transfer case might be the problem.

The Selectable Four Wheel Drive (S4WD) Front Axle consist of the following components:
• Differential Carrier Housing
• Differential Case Assembly
• Inner Axle Shaft
• Intermediate Shaft Bearing Assembly (located on the right side of the oil pan)
• Electric Motor Actuator
The front axle on Selectable Four Wheel Drive (S4WD) model vehicles uses a disconnect feature mounted on the right side of the oil pan in order to engage and disengage the front axle. When the driver engages the 4WD system, the Transfer Case Control Module sends a signal to the electric motor actuator to energize and extend the plunger inside. The extended plunger moves the clutch fork and clutch fork sleeve across from the clutch fork outer gear that is splined to the right side wheel drive shaft to the clutch fork inner gear that is splined to the inner axle shaft. The locking of the two gears allows the axle to operate in the same manner as a semi-floating rear axle. A propeller shaft connects the transfer case to the front axle. The differential carrier assembly uses a conventional ring and pinion gear set to transmit the driving force of the engine to the wheels. The open differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when going around corners and premature wear on internal axle parts. The ring and pinion set and the differential are contained within the carrier. The axle identification number is located on top of the differential carrier assembly or on a label on the bottom of the right half of differential carrier assembly. The wheel drive shafts are completely flexible assemblies consisting of inner and outer constant velocity CV joints protected by thermoplastic boots and connected by a wheel drive shaft.

How To Install Repair Replace 4x4 Front Axle Actuator Chevy Trailblazer...

The actuator under the battery runs the engagement of the front Diff .If 4 - wheel low is working and high is not then that is a linkage adjustment problem at the transfer case or a internal problem with in the transfer case not the transmission . Those transfer case are not that expensive from a salavage yard if that ends up being your problem and they are not that hard to change ... Alot easier then the transmission

Sounds like the truck is in 4 wheel drive, try turning the front driveshaft, it should turn freely if it is in 2wd otherwise you may have transfercase problem or your front diff is locked in

an accuator either on the transfer case or on the front differential

it could be a bad acuator on the transfer case or the front diff

Place vehicle in 4wd (high or low). This will hold the front drive shaft still for the rest of the test. Jack up the front end of the vehicle. Remove the actuator. Have a buddy spin the right front wheel while you use a long punch or screwdriver to try to manually engage the diff. The left front wheel should spin in the other direction if the diff is good. Also before you check the diff you need to grab the front driveshaft and make sure it is locked, If it spins freely when the truck is in park and in 4wd with the front end raised then problem is in transfer case. If you can't make the diff engage manually with punch then the problem is in the diff. If front diff engages manually then the problem is the actuator. Hope this helps..