Transfer Case Problems of GMC Sonoma

Purchased truck in 2006. Mileage at 48,000. Trouble starting, fuel pump replaced. Oil cooling lines replaced. Subsequently, automatic transmission slips from 2 wd to 4 wd for no apparent reason. I have noticed that this problem occurs when accelerator is not depressed, and wheels are turned, to turn a corner or to turn into/out of a driveway. Usually there is a depression in path as well, I. E. Curb/dip at driveway entrance, pothole, etc. Engine is not always cold; sometimes shifts at end of trip, sometimes at beginning, no adverse weather conditions.

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2001 4wd 4. 3 GMC Sonoma, 53k miles, no known events leading to failure, without warning transmission failure, loss of first gear and reverse, almost caused accident do to unexpected deceleration. I have replaced transfer case (where it was making much noise) but this did not correct problem. By far this truck is not "professional grade" as their advertising claims!.

I currently own a 2002 GMC Sonoma zr5 4wd pickup. Shortly after purchase the vent controls for the a/c unit started to malfunction. This did not seem to be a big deal until last week when I was told the problem had been traced to a vacuum module on the transfer case that controls switching in and out of 4wd. The dealer replaced to defective part and returned the vehicle to me. On Monday, I was driving home on the interstate, took my foot of the gas and started braking for the off ramp. As I was coming around the sharp curve on ramp, the transfer case tried to switch from 2wd to 4wd. As you may be aware, trucks do not handle the same in 4wd. My concern is the fact that had the roads been wet, it very possible that the jerk of switching to 4wd on a sharp curve would cause the truck to lose traction and spin out of control. It should also be noted that dealer has informed me that it may take up to three weeks to obtain the parts and repair damage to my transfer case and a/c controls caused by this defect but the factory has made no modifications to the control module and this may happen again at any time. I have informed the dealer that I will not accept the truck back until GMC can assure me that this defect has been corrected and warranty any future problems that may arise. The truck currently has 24,000 miles but only had about 12,000 when the first module started malfunctioning.

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The transfer case leaked, which caused the actuator to short and leaked oil internally. Oil was seen in the lighter, ash tray and on the passenger side floor.