Standard (open) carrier
Here's how it works:
The Main PartsCarrier – The metal case that houses the internal gears.Ring Gear – Bolts to the outside of the carrier and is driven by the pinion gear.Spider Gears (Pinion Gears) – Small gears inside the carrier that rotate on a cross shaft.Side Gears – Splined to the axle shafts and mesh with the spider gears.How a Standard Carrier OperatesDriving Straight
When both rear wheels have equal traction and the vehicle is traveling straight:
The pinion gear turns the ring gear.The ring gear rotates the carrier.The spider gears do not rotate on their shaft—they simply revolve with the carrier.Both axle shafts receive equal torque and turn at the same speed.Turning a Corner
When the vehicle turns:
The outside wheel has to travel farther than the inside wheel.The spider gears begin rotating on their shaft.This allows one side gear (and axle) to spin faster than the other.Both wheels still receive torque, but at different speeds.
This ability to let the wheels rotate at different speeds is why it's called an open differential.
AdvantagesSmooth and quiet operation.Inexpensive and reliable.Minimal tire wear during turns.Requires very little maintenance beyond regular gear oil changes.Disadvantages
The biggest drawback is traction.
If one tire loses grip (ice, mud, gravel, or one tire off the ground):
The standard carrier sends torque to both axles, but the amount of usable torque is limited by the wheel with the least traction.The slipping wheel spins easily.The wheel with good traction may receive too little torque to move the vehicle.
This is why a vehicle with an open differential can get stuck even when only one tire is on a slippery surface.
Standard Carrier vs. Posi CarrierStandard (Open) Carrier Posi/Limited-Slip CarrierAllows wheels to turn at different speeds Allows different wheel speeds while limiting excessive slipExcellent for normal street driving Better traction on slippery surfacesIf one tire slips, it spins Sends more torque to the tire with better tractionLowest cost More expensive and contains clutches, gears, or other torque-biasing components
In simple terms, think of a standard carrier as a traffic director. It normally splits power between both wheels while allowing them to rotate at different speeds in a turn. However, if one wheel loses traction, it can't redirect extra power to the wheel with grip—that's where a limited-slip (posi) carrier has the advantage.
The Main PartsCarrier – The metal case that houses the internal gears.Ring Gear – Bolts to the outside of the carrier and is driven by the pinion gear.Spider Gears (Pinion Gears) – Small gears inside the carrier that rotate on a cross shaft.Side Gears – Splined to the axle shafts and mesh with the spider gears.How a Standard Carrier OperatesDriving Straight
When both rear wheels have equal traction and the vehicle is traveling straight:
The pinion gear turns the ring gear.The ring gear rotates the carrier.The spider gears do not rotate on their shaft—they simply revolve with the carrier.Both axle shafts receive equal torque and turn at the same speed.Turning a Corner
When the vehicle turns:
The outside wheel has to travel farther than the inside wheel.The spider gears begin rotating on their shaft.This allows one side gear (and axle) to spin faster than the other.Both wheels still receive torque, but at different speeds.
This ability to let the wheels rotate at different speeds is why it's called an open differential.
AdvantagesSmooth and quiet operation.Inexpensive and reliable.Minimal tire wear during turns.Requires very little maintenance beyond regular gear oil changes.Disadvantages
The biggest drawback is traction.
If one tire loses grip (ice, mud, gravel, or one tire off the ground):
The standard carrier sends torque to both axles, but the amount of usable torque is limited by the wheel with the least traction.The slipping wheel spins easily.The wheel with good traction may receive too little torque to move the vehicle.
This is why a vehicle with an open differential can get stuck even when only one tire is on a slippery surface.
Standard Carrier vs. Posi CarrierStandard (Open) Carrier Posi/Limited-Slip CarrierAllows wheels to turn at different speeds Allows different wheel speeds while limiting excessive slipExcellent for normal street driving Better traction on slippery surfacesIf one tire slips, it spins Sends more torque to the tire with better tractionLowest cost More expensive and contains clutches, gears, or other torque-biasing components
In simple terms, think of a standard carrier as a traffic director. It normally splits power between both wheels while allowing them to rotate at different speeds in a turn. However, if one wheel loses traction, it can't redirect extra power to the wheel with grip—that's where a limited-slip (posi) carrier has the advantage.