Rearend Rebuild - Rebuild Your Own Quick-Change Rear

Given enough time and use, everything on your car will eventually wear out, or worse, break. And of course, Murphy's Law dictates that the component on your race car that you least expect to fail will give out on the night that a win looks like a sure thing.

Most gear specialists recommend inspecting and rebuilding your rearend every off-season, even if everything goes perfectly (and how often does that happen?). You should rebuild more often if you are racing a high-horsepower car in long-distance races. And whenever you suspect you may have damaged the rearend-especially if you have been in a wreck and a rim on a rear tire is bent or flattened-you should perform an inspection before the next race to ensure you won't take to the racetrack with a rearend that's likely to fail.

We traveled to Tiger Rear Ends, in Mount Ulla, North Carolina, to get a better idea of what should be done when rebuilding a quick-change rear. Along with the Ford 9-inch, a quick-change rear is easily the most popular type of rearend used in auto racing. The beauty of the quick-change is that the gears can be changed quickly and easily to achieve a wide array of final gear ratios. There are different companies making quick-changes, and each has its own design, but they all work on the same principles and many of the processes detailed here are applicable to all makes of quick-change rearends.

Unless there are significant problems, most rebuilds include pulling and inspecting both axles, removing at least one axle tube and bell, removing the locker or spool and pinion gear, and even rebuilding the differential if necessary. A fully assembled centersection is the most complex component of the entire rearend. It includes the pinion gear, the yoke, the jackshaft, and several sets of bearings-all of which must be installed with the correct amount of crush. Crush is the amount of preload on the differential bearings. Also, before you can even get started with a complete disassembly of the centersection, its housing must be baked in an oven to open up the housing bore diameters. Fortunately, Wayne Ingram, one of Tiger's gear specialists, says that most quick-changes can go through a few rebuild cycles without needing the centersection disassembled. And when it is necessary, it is often sent to a specialist, such as Tiger, that has the setup necessary to perform the task. For most in-shop rebuilds, like the one we tackle here, the centersection is left alone.

When you begin the teardown, take a moment to check your gear oil. The lubricant in a rearend that has been run too hot will have a distinct "burnt" smell. It is hard to describe in print, but even if you've never smelled it before it is safe to say that once you do you will know exactly what we're talking about. The smell is more noticeable in mineral-based lubricants, which are more sensitive to temperature, but it can also be present in synthetic lubricants. It is a good idea to run the lubricant through a fine mesh strainer to see if there is any metal debris. If that's the case, you must find the culprit: It is usually a gear or bearing gone bad.

Teardown requires pulling the bearing from the spool or locker inside the rearend. Without the proper tools, it is very easy to damage the bearing races, so make sure you have the correct tools, such as a bearing puller. Tiger sells a rearend rebuild toolkit that includes everything needed to tear down just about any quick-change rear and properly measure lash on the rebuild.

Finally, visually inspect the rest of the components. Check all gears for discoloration. Specifically, look for a blue or brown sheen, which can be a sign of overheating. In addition, be on the lookout for chips, hairline cracks, and excessive wear. Make sure all bearings spin freely without grinding or catching. Inspect your seals for cracks or deterioration and follow that up by inspecting both bells and the centersection for cracks or other damage. Once you have identified all the parts that can be reused, thoroughly clean them to prepare for the rebuild.