Tech Corner: Breaking in New Gears

Understand the vital process of breaking in new ring and pinion gears.

There are a million and one reasons to change your ring and pinion. Whether it be on account of a big, high-performance camshaft or an oversized set of wheels and tires, the final drive gear ratio is something every builder is going to have to change at some point.

It’d be nice to avoid messing with the ring and pinion, but you really can’t. That’s because the gear ratio the vehicle comes with is carefully selected with consideration of the combination of parts and typical driving conditions around town and on the highway. Moving to specialty driving or changing that combination throws everything out of balance and, as a result, performance suffers. Engines with bigger cams fall out of optimal RPM ranges and run poorly when cruising, those with bigger tires see throttle response fall off, and so on. Moving to the right ring and pinion for the combination restores and may even radically improve performance in those instances.

The only problem is that the best results are heavily reliant on setting off on the right foot. After a professional installation, you need to do your part to run new gears through a break-in period. Luckily, that’s a lot simpler than you might think. You just need to make sure you follow the right steps to ensure you avoid having to invest in yet another new set of gears.

Why do I need to break in my ring and pinion?

The ring and pinion are a gear set. Naturally, that means they see constant friction, and throughout the first few miles, those gears will wear into each other. As they do, any roughness or imperfections on the gear teeth will be rapidly stripped away. Even if the gears come out of the box perfectly smooth, variables such as bearing preload, backlash, and wear patterns set by the installer make excessive wear in the initial cycles unavoidable.

The whole process also produces a ton of heat. Extreme heat will break down the gear oil, leading to catastrophic failure. A proper break-in avoids the matter altogether and gives you the chance to rid the rear end of the excess metal shavings produced during the initial mating of the gears.

How do I break in new gears?

Breaking in new gears isn’t all that complicated. Essentially, the idea is to avoid abusing and overheating the gears for the first 500 to 1,000 miles. That means no burnouts or setting land speed records – at least, not if you want to do those kinds of things for a long time without having to worry about replacing the ring and pinion.

To start, you want to drive the vehicle at lower in-town speeds for about 20 minutes. Then, you want to take a break for 30 minutes to an hour so that the gears can cool down, then repeat the cycle two to three times. After a few around-town cycles, you need to get out on the highway. The process is similar in that you’ll run the vehicle for about 15 miles, then pull over and let the gears cool, repeating the cycle two to three times. If you’re using the vehicle to tow, you need to repeat this cycle the first time the vehicle is used for towing.

Once all of that’s completed, it’s a simple matter of driving normally for another 500-1,000 miles. Then, you’ll need to replace the gear oil and put the whole break-in procedure behind you.

Choose the Right Fluid

There’s no harm in using the best lubricants you can buy for the break-in period, but it’s not necessary. In fact, you’re better off using cost-effective conventional oils for the process, as they’ll be disposed of in short order anyway.

The only time to use better synthetic oils is for bigger, heavier applications that produce more heat because the more uniform molecular structure of synthetic oils better resists breaking down. Of course, you still want to use a friction modifier for a limited-slip differential if you’re using one.

The First 500 Miles…

It’s a good idea to have a differential expert replace the oil and inspect your differential after the initial break-in period. However, if you’re reading this, you’ll likely be doing it yourself.

The oil is going to be black and likely filled with some metal shavings. That’s okay, though. You’re expecting the gears to wear into each other, producing both. However, there is such a thing as too much. If there’s a ton of metal shavings built up in the case, then it’s an indication something’s gone wrong or something wasn’t installed right. You’ll need to tear it apart and start over.

That’s a worst-case scenario, though. For now, it’s the right time to inspect the wear pattern on the teeth, double-check the backlash, and make sure there’s no slop in the bearings. If that all checks out, all that’s left is to refill the differential and carry on as normal.

Motive Gear for When It Matters

You’ll have a hard time working with anything other than Motive Gear when modifying your differential. The brand has been in the game for over 30 years and has thoroughly mastered the realm of ring and pinions, setting the standard for this corner of the industry. Quality is made possible with unrivaled expertise, promised with the use of premium materials and rigorous quality control practices, and reinforced with a real warranty.

From start to finish, Motive Gear’s got you covered. The company’s gear ratio calculator helps you determine which gears are the right fit for your application. An impressive catalog ensures you can get the ring and pinion your setup commands, while installation kits help you put them where they belong.

To learn more about Motive Gear, visit: https://www.motivegear.com/.