Gear break-in consists of controlled heat cycling of the gear set in a way that properly seasons or hardens the gear’s contact surfaces. It is a series of test drives. These critical first few miles of drive time can be the difference between a gear-melting headache and years of carefree driving. Failure to properly break-in your gear set can result in damaged, failing gears, and a complete re-do.
Once the wrenches have been laid down and the gears have been properly installed with pinion depth, backlash, and preload correctly set there’s still more to do. The break-in process is really important if you want to have your gears last a long time and perform the way you want them to.
The First Drive
In the first couple of miles you will want these to be in-town speeds, 15 to 20 mph. Drive for 20 minutes or so, let the diff cool off for about a half an hour, and then repeat the process. Next time you drive your vehicle you’ll want to do some freeway runs. Drive about 15 miles, then pull over and let the drivetrain cool down for about 20 minutes and do this for about 45 miles or so. It may seem like a headache, but it is worth it to ensure the gears are broken in properly instead of burning them up and creating a bunch of metal sledge in your differential.
The next important component is to ensure you have proper lubricants. For the first 500 miles run 80W-90 conventional oil, drain it, and then refill the diff. HYDUN recommends a non-synthetic oil if your set-up features a Dura Grip clutch-type limited slip differential. If you’re running a helical LSD or a locker, synthetics are great for those applications.
Break-In For Rigs That Tow
Towing with your vehicle or using it for extreme off roading adds additional pressure to the pinion and can slightly change its position on the ring gear teeth. This means you are essentially hardening a new spot on the gear. Therefore, we strongly encourage drivers to follow the same break-in procedure while either towing, hauling, or driving off road. Even if you’ve already broken in the gear set with no addition load follow the same speeds and distances of your previous break-in drives.
Start with in-town speeds of 15 to 20 mph, cool down, and repeat. Then hit the freeway and drive 15 miles at 45 to 50 mph, cool down, and repeat for 45 miles. Long distance hauling is the killer for any ring gear set as you are constantly generating heat without cooling which will break down the gear oil and burn up the gear surface. This is why we recommend a gear oil change after the first 500 miles.
If you want to protect your investment and get the best performance out of your gears, then proper break-in is critical. Following the guidelines outlined here will ensure you get the expected results.