Things To Consider In Circle Track & Road Racing

The main thing to consider when building a rearend for any type of racing is strength and durability. After spending tens of thousands of dollars on the engine and transmission, why skimp on cheap rearend parts?

Any rearend that transfers a lot of power will get hot. The only way to make the rearend live is to keep the oil from deteriorating and keeping it cool. The best way to keep the oil cool is to pump it through a cooler system that has adequate oil flow and air flow. This requires a pump, a system to turn the pump, oil lines, extra oil volume (and often an external sump), a good radiator, and ducting or placement for adequate air flow through the radiator. The difference in bearing and gear life with or without a good cooler system is amazing.

Some people do not like using synthetic oils. We have found that differentials without an oil cooler last far longer and have a much smaller chance of burning up the gear-set when synthetic oil is used. Crude oil is a lot cheaper, and works well if it does not get too hot, but synthetics work a lot better for rearends without a cooler.

Safety wired bolts are not easy to work with. They take longer to assemble and the bolts are expensive to buy or drill. However, having a bolt back out costs a lot of time and money, especially if it costs points or a win. Ring gear bolts are the most important for safety wiring, but some insist on wiring the main cap bolts and pinion support bolts as well.

Use red Loctite on all ring gear bolts, all pinion nuts, main cap bolts on severe duty use, and on pinion support bolts on severe duty use. Always clean the bolt and hole threads with a non-oily cleaner (brake-clean spray works well) before applying the Loctite. Put a drop or two on the end and it will work its way up the threads as the bolt is inserted.

A crush sleeve works great for most street cars and production vehicles, but a race rearend should always use a solid spacer and shims. A spacer machined from billet steel is far superior to one cut from tubing. The best 9″ Ford spacers use two pieces cut from billet that enclose the shims completely and keep the bearings from wearing down the fragile shims. The pinion yoke should not be re-installed after removal when a crush sleeve is used. When using a solid spacer, the pinion yoke can be removed and installed over and over without affecting the bearing preload.

There are a few manufacturers other than Timken who make good bearings, but Timken has always been the most consistent and has always been the standard that others are judged by. It is also cheap insurance to install new bearings any time the old bearings show wear or heat damage.

Tools set man apart from the rest of the animal kingdom. Using the right tools not only makes the job easier, it also ensures the rearend is assembled correctly and completely. A good, solid tool for turning the side adjusters is absolutely necessary. It takes about 150 ft lbs of torque to tighten a 9-inch Ford adjuster correctly. Any less will allow the ring gear to flex away from the pinion and the gear-set will not live as long. An accurate and easy-to-read dial indicator is necessary for properly measuring the backlash. An accurate inch/lbs torque wrench is needed to set the pinion bearing preload correctly.

These pinion seals are best for racing. They are made from Viton® Fluoroelastomer, well known for its excellent (400°F/200°C) heat resistance. Their exceptional mechanical stability makes them ideal for severe operating conditions.

The main thing a race rearend needs to live is good lubrication. Hot, dirty oil will end the life of a rearend faster than just about anything else.

Cleanliness when assembling the rearend is essential to long life. Dirt, dust, metal filings, and any number of other foreign debris will affect the rearend life. A good rearend mechanic keeps their bench and work area free of any dirt or contaminants that can affect the rearend. This may seem obvious, but I see the issue of cleanliness missed more often than not.

Bearings are more important to gear life than most mechanics realize. When it comes to the time and money to replace bearings, most people would choose not to go through the trouble. There are many things that can damage a bearing and lead to failure, even if the bearing doesn’t LOOK bad. Heat is probably the biggest killer of bearings in a racecar rearend. Scratches during assembly can lead to premature failure. Pinion bearing preload is VERY critical and either too much or too little can lead to bearing and/or gear failure. Whenever the pinion support is removed or the rearend is disassembled, the pinion bearing preload should be measured (with an accurate inch pounds wrench) and adjusted.

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