The NV4500 is a highly regarded five-speed manual transmission manufactured by New Venture Gear. Dodge and General Motors began installing slightly different variations of the NV4500 in their trucks in 1992. The four-wheel drive versions are also popular transmission swaps for Jeep, Toyota and Ford off-road enthusiasts. While changing the gear oil in the NV4500 is a simple process, the cost of the required synthetic makes the change fairly expensive. A common-sense approach would be to follow the recommendations of either the vehicle or transmission manufacturer as to the proper interval.
Drive the vehicle until the transmission is at operating temperature. Park on a solid, even surface. If possible, work on the vehicle without raising it off the ground. Otherwise, jack the vehicle up and support it safely on jack stands, making sure the transmission remains level.
Put an oil drain pan under the transmission. Remove the fill plug and set it aside. Remove the drain plug. Allow the oil to drain thoroughly. Clean the drain plug with a rag and reinstall it in the case. Move the drain pan out of the way.
Insert the suction tube of a manual oil pump into a container of fresh gear oil. Place the pump outflow tube into the transmission fill hole. Use the manual pump to fill the transmission case.
Stop pumping when oil begins to trickle from the fill hole. Most versions of the NP4500 will hold nearly a gallon. Clean the fill plug and reinstall it in the transmission case. Wipe up any spilled oil with a rag.
