DIFFERENTIALS 101Updated 2 months ago

What a Differential Is

At Dynatrac, we see the differential as the heart of the axle. It’s the mechanical component that takes the rotational power from the driveshaft and splits it out to your wheels, allowing for smooth turns by letting each wheel rotate at a different speed. In a solid axle, it also plays a massive role in durability and torque handling, especially in off-road and heavy-duty applications.

Ring and Pinion – The Gear Set That Does the Work

The ring and pinion gear set is what translates the spinning motion from your driveshaft (via the pinion) into usable torque at the axle shafts (via the ring gear bolted to the carrier). Here’s what we focus on when it comes to gear sets:

• Gear Ratio: This determines your mechanical advantage. A 4.10:1 gear ratio means the pinion rotates 4.10 times for every 1 revolution of the ring gear. Lower ratios (numerically higher, like 5.38) give more torque but less top-end speed, which is ideal for rock crawling and big tires. Higher ratios (numerically lower, like 3.73) are better suited for fuel economy and highway cruising.
• Strength: Our gears are manufactured with premium materials, heat-treated for strength, and cut for the highest tolerances. We often recommend thick-cut gears for re-gearing on carriers that don’t need to be replaced — maintaining proper pinion depth while keeping the carrier the same.

Gear Installation Kits – Don’t Skip These

When we build or re-gear an axle, we always use a Master Install Kit. These include:

• Carrier Bearings
• Pinion Bearings
• Pinion Seal
• Shims (used to set pinion depth and carrier preload)
• Crush Sleeve or Solid Spacer
• Ring Gear Bolts
• Gasket or RTV

Every part here is critical for setting proper gear mesh and ensuring long-term durability. Subpar components or skipping steps here can lead to gear whine, overheating, or catastrophic failure.

Gear Setup: Mesh Pattern, Backlash, Preload

Setting up gears properly is everything. Here's what we dial in during a build:

• Pinion Depth: This is adjusted with shims behind the pinion bearing. It affects how deeply the pinion teeth contact the ring gear.
• Gear Mesh Pattern: Once we apply marking compound and rotate the gear, we analyze the contact patch. It needs to be centered on the tooth — not too deep, not too shallow. That’s our window into proper setup.
• Backlash: This is the gap between the ring and pinion teeth. Measured with a dial indicator, typical spec is around 0.006"–0.010". Too tight = heat and noise. Too loose = gear slap and eventual failure.
• Bearing Preload: This keeps everything under the correct tension — especially the pinion. Done right, it prevents movement and wear under torque.

Carriers, Spider Gears & Lockers

Inside the differential housing, the carrier supports the ring gear and houses the spider gears. Spider gears allow one wheel to rotate faster than the other when cornering — essential for road use.

When you’re upgrading for off-road use, this is often what we change. Here's what happens:

• OEM Open Carrier: Has spider gears, good for daily driving, but one tire will lose all traction when things get slippery.
• Limited-Slip Differentials (LSD): Adds friction or clutches to bias power to the tire with more grip. Good for mild off-road.
• Aftermarket Lockers: These replace the entire carrier. Whether it's a mechanical locker, selectable locker (like ARB or Eaton E-locker), or automatic (like Detroit Locker), it eliminates the spider gears and allows both tires to receive 100% of the torque when locked.

At Dynatrac, we often set up our axles with Detroit Lockers, ARBs, or Eaton based on customer use — all gear-driven or air/electric-actuated solutions that replace the OEM-style carrier entirely. They’re housed inside our high-strength nodular iron housings and supported by massive carrier bearings.

All the Components Inside a Dynatrac Solid Axle Differential

Let’s lay it all out from front to back:

1. Pinion Yoke/Flange – Connects to driveshaft
2. Pinion Nut – Applies preload and torque to pinion
3. Pinion Bearings (inner/outer) – Maintain alignment under load
4. Pinion Seal – Prevents gear oil leaks
5. Pinion Gear – Transfers rotation to ring gear
6. Carrier Bearings – Keep carrier tight in housing
7. Carrier (or Locker) – Supports ring gear and distributes torque
8. Spider Gears (if open or LSD) – Allow for wheel differentiation
9. Ring Gear – Mates with pinion to rotate the carrier
10. Shims or adjusters – Used to center and preload the carrier
11. Axle Shafts – Transfer power to wheels

Why Dynatrac Builds It Better

• We precision-machine everything in-house in the USA, so tolerances are exact.
• Our housings support massive gear sets and oversized bearings, reducing deflection under high torque.
• We can match gear ratio, carrier style, and axle shaft strength to your vehicle weight, tire size, terrain, and use case.
• And when it comes to re-gearing — we offer thick-cut gears, nodular cases, upgraded fasteners, and install kits that eliminate failure points.