Lowering hiway engine RPM.
Some serious homework is needed to achieve the desired effect. Go to a salvage yard and seek all information available. Most salvage yarsds can intelligently give advise on what gears or complete rear axle assemble will fit what vehicle. With some planning, good tools and talent nearly any rear axle can be installed. To make an informed decision, all the factors must be noted. The short list of information needed are, engine type, type of transmission, weight of vehicle, desired vehicle top speed, desired engine maximine rpm and money required for parts and installation. Some rear axles are very simple and have very low costs. The most important part of any task is the plan. One man's trash is another man's treasure. Frank