A "posi rear," often short for "positraction rear end," refers to a type of differential in a vehicle's rear axle that helps distribute power to the rear wheels and helps them spin at the same speed.
Understanding Positraction Differentials
Here's a breakdown:
- Function: When one wheel starts to slip (for example, on ice or loose gravel), a positraction differential redirects more power to the wheel with better traction.
- Benefit: This prevents the wheel with less traction from spinning freely, allowing the vehicle to maintain forward momentum.
How it Works:
Instead of allowing all the power to go to the wheel with the least resistance (which happens in a standard "open" differential), a positraction differential:
- Detects Wheel Slip: The differential senses when one wheel is spinning faster than the other, indicating a loss of traction.
- Redirects Power: It uses various mechanisms (clutches, gears, etc.) to limit the amount of differential action, effectively sending more torque to the wheel with grip.
- Improved Traction: This helps the vehicle move forward even when one wheel is on a slippery surface.
Advantages of a Posi Rear:
- Enhanced Traction: Significantly improved traction in slippery conditions (snow, mud, ice).
- Improved Off-Road Performance: Enables better control and maneuverability in off-road situations.
- Better Acceleration: Can provide quicker and more consistent acceleration on surfaces with uneven grip.
Disadvantages of a Posi Rear:
- Increased Cost: Posi differentials are generally more expensive than standard open differentials.
- Potential for Noise/Harshness: Some posi differentials can produce noise or feel harsh during tight turns.
- Increased Maintenance: Some types may require special lubricants or more frequent maintenance.
