1991 GMC Rally Wagon 3500 Problems
RepairPal has identified the most common problems with the 1991 GMC Rally Wagon 3500 based on complaints from actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.
Our technicians highly recommend that the transmission is serviced every 30,000 miles to avoid problems and maintain optimal operating order. As for the 4L80-E Transmission (Diesel adn 7.4L gas engine), Transmission fluid may leak through the electrical connector on the side of the transmission, damaging the wire harness and causing the transmission to shift erratically. Our technicians tell us there are updated shift solenoids, an internal transmission harness, and a connector pigtail available to correct this fault.
An engine vacuum leak may develop from the throttle body gasket causing a higher than normal idle speed. Failed gaskets should be replaced.
A coolant leak may develop from the water pump. This can result in an engine overheating condition. A leaking water pump will require replacement.
The intake manifold gasket may develop and external engine oil or coolant leak. In some cases, an internal coolant leak may occur causing coolant to mix with the engine oil. Running the engine with a coolant/oil mix may result in engine damage. Replacing the intake manifold gasket should correct this issue.