how do I change rearend oil
rear differinal on 1990 GMC S15
simple. unbolt the 10 attaching bolts on the housing and catch the oil in a pan. get a cover gasket and install. get the correct fluid and the proper amoount and add at the port on the drivers front of the differental. you will need a 3/8 rachet with a 3 inch extension to remove fill plug. fill oil to the level of the plug.