I have an issue that is leaving me stumped.

While in 2-HI, when I start out from a dead stop, at about 5-10 mph I hear a "groaning noise" under the dash on the left side. It sounds like it is coming from inside the vehicle, not underneath. It is subtle but definitely there. At the same time I see a dip in the voltmeter and if the headlights are on the lights will flicker once. It does it almost every time I start moving forward from a dead stop.

I do not get any messages on the dash but I thought it was the traction control kicking in. I tested that theory by disabling the traction control and the noise, voltage drop, and headlight flicker all go away. I also checked 4WD and if I have the vehicle in Auto 4WD or in 4-HI it does not happen at all.

I have cleaned the wheel speed sensors and that did not make it go away. I have also replaced the 4WD selector switch and cleaned the two ground wires located underneath on the driver's side. My next plan was to have the wheel speed sensors checked to make sure one is not faulty.

My Tahoe is a 2005 Z71 with 120,000 miles on it. Hasn't been beat up too bad and has very little off road time.

Has anybody ever experienced this and if so, what was the fix?? Aside from the obvious of not putting it in 2WD or turning the Traction Control off.

It's driving me nuts......

 

In case anybody was following along.

Left front wheel speed sensor was faulty. Replaced it and problem has gone away.....