Two problems related to transfer case have been reported for the 2001 GMC Sonoma. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2001 GMC Sonoma based on all problems reported for the 2001 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.
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!.