The GMC Jimmy drive belt is a single, nylon-reinforced belt that turns all the accessories on the front of the engine. The belt is kept tight with the use of a spring-loaded automatic belt tensioner but after use, the belt will stretch and even the tensioner will not keep it tight. When this happens, replace the belt with a new one. Replacement serpentine belts are available from any auto parts retailer or through the GMC dealership.
Find and disconnect the negative battery cable from the negative battery terminal of your Jimmy. Loosen the clamp bolt on the cable end with a wrench and lift the cable off, setting it out of the way while you work.
Locate the serpentine belt tensioner. There are two possible locations in the Jimmy for these tensioners. One is low on the front of the engine and the other is high on the front of the engine. In either case, it is mounted near the centerline of the engine.
Place a socket on the center bolt that holds the idler pulley to the tensioner arm then turn it with a ratchet, moving it counterclockwise. Remove the belt from the engine pulleys and throw it away. You will not reuse it.
Install a new belt on all the pulleys, paying close attention to the path over the pulleys. If the path is wrong, the belt will turn the accessories backward causing damage to them. If you are unsure about the path, there is a diagram on the radiator support under the hood that will help you.
Rotate the belt tensioner clockwise to tighten the belt then remove the socket and ratchet from the tensioner. Install the negative battery cable on the battery and tighten the clamp bolt with a wrench.
