Two problems related to transmission gear slipping have been reported for the 1998 GMC Jimmy. The most recently reported issues are listed below.
Transmission slipped and lost power while towing 4200 pound RV, a unit well under the towing capacity of the GMC Jimmy. Transmission got hot and slipped with noticable loss of power. Odd odor came from engine compartment, also. "service engine soon" light came on during fuel stop. We thought it was due to fuel cap or gasoline used. Contacted dealer upon return from trip and had item scheduled for check on mon 6/7/1998. Had transmission oil and filter changed and mechanic noted oil excessively black. Check engine light monitor indicated tranmisssion had overheated twice. Recommendation was to drive slower, change oil and filter more often, get a wind resistance deflector for towing vehicle. Vehicle has towing package with extra transmission oil coller rated at over 10,000 pounds towing capacity. Salesman, who was a previous RV dealer/salesman, assured us when we purchased the vehicle that it was more than adequate to handle the towing of the RV (26 foot dutchman lite, rated at 4200 pounds). Afraid that transmission will fail again and we will become stranded. Wife, who drives vehicle daily, also noted that transmission felt like it was slipping periodically when driving without any load attached to the veheicle. Am overly concerned now that I also have a 1998 GMC sonoma with same engine, trnasmission, and towing capacity for alternate for towing RV, and that it's transmission may experience the same symptoms.
The transmission light illuminated on the dashboard, and when the weather was hot transmission slipped. . . . .