Upgrading a vehicle with larger tires is common among off-road enthusiasts. Larger tires allow you to venture into territory that would be unreachable with factory tires and stock suspension systems. Larger tires do have some drawbacks, however. Larger tires are more expensive, require an upgraded drive train to provide appropriate support and potentially throw off the calibration of the speedometer. With a tire size chart, a new speedometer gear with the proper tooth count can fix the problem.
Determine the appropriate speedometer gear to replace the stock unit. Charts are available online that will allow you to make the correct choice. The number of teeth on the new gear will be determined by the size of the new tire.
Locate the speedometer gear housing on the tail side of the transfer case. There will be a retaining clip holding the speedometer gear into the housing. Put on the gloves to keep your hands protected from any potential grease and fluid.
Use the ratchet and 1/2-inch socket to remove the bolt that holds the retaining clip to the transfer case housing. Set the retaining clip aside for re-installation.
Pull the speedometer gear out of the socket. Grasp the gear with a firm grip and pull the metal shaft with the gear from the housing.
Install the new speedometer gear into the speedometer fitting. Insert the gear back into the transfer case housing, being careful to properly align the housing. Marks on the transfer case will tell you how far to turn the socket.
Install the retaining clip and bolt into the transfer case with the ratchet and socket.
