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Maximize Towing With the 5.9 Cummins Diesel

Towing Capacity

The 5.9 liter Cummins turbo diesel engine has been a workhorse in Dodge Ram heavy duty trucks for many years. This inline 6 cylinder engine provides incredible torque for towing large loads. But how much can you realistically tow with the 5.9 Cummins? Here’s an in-depth look at optimizing towing capacity.

5.9 Cummins Overview

The 5.9 liter Cummins was introduced in 1989 as an option for Dodge Ram pickup trucks. It quickly earned a reputation for reliability and capability. The engine underwent several upgrades over the years:

  • 12 valve (1989-1998)
  • 24 valve (1998.5-2002)
  • Common rail (2003-2007)

Horsepower and torque steadily increased with each generation:

  • 12 valve: 160-215 hp, 400 lb-ft torque
  • 24 valve: 235-305 hp, 505-610 lb-ft torque
  • Common rail: 305-350 hp, 610-650 lb-ft torque

The later common rail engines provide immense torque for pulling heavy loads. But even the 12 valve and 24 valve engines have impressive tow ratings.

Towing Capacity Basics

Towing capacity is determined by several factors:

  • Engine power and torque – More torque at low RPMs improves pulling power.
  • Transmission and rear end gearing – Lower gears increase torque multiplication.
  • Chassis and suspension – Heavier components improve stability under load.
  • Braking system – Larger brakes with integrated trailer brakes.
  • Tire size and load range – Larger tires spread the weight over more contact patch.

Manufacturers determine max towing capacity based on the chassis, drivetrain, and hardware limitations. But real world towing can depend on terrain, weather, and maintenance.

Optimizing 5.9 Cummins Towing

Here are some tips to maximize your towing capacity with a 5.9 liter Cummins:

Truck Configuration

  • Dually vs single rear wheel – Dual rear wheels provide more stability for heavier loads.
  • 2WD vs 4WD – 2WD models allow 300-500 lbs more capacity.
  • Manual vs automatic transmission – Manual transmissions have higher capacities.
  • Rear axle ratio – Lower ratios like 4.10 multiply torque for towing.

Choose the optimal truck configuration for your needs. For occasional towing, 2WD and an automatic may suffice. For frequent heavy towing, opt for a dually with 4WD, manual, and lower gears.

Performance Modifications

  • Diesel fuel pump – Higher capacity for increased fuel delivery under load.
  • Injectors – Larger injectors flow more fuel for power gains.
  • Turbocharger – A larger turbo increases boost and airflow.
  • Exhaust – Improves airflow out of the engine.
  • Programmer – Custom tunes to optimize fueling for mods.

Carefully matched performance upgrades can add 50-100 hp and 100-200 lb-ft torque. This extra power improves towing capacity and reduces transmission strain.

Drivetrain Protection

  • Transmission cooler – Prevents overheating of automatic transmissions.
  • Synthetic transmission fluid – Handles heat better than conventional fluid.
  • Auxiliary transmission cooler – Adds more cooling capacity for heavy loads.
  • Transmission temperature gauge – Monitors fluid temp to prevent overheating.
  • Torque converter lockup switch – Locks converter in each gear to reduce slippage.

Protecting the drivetrain prevents the transmission from being the weak link when towing near capacity.

Boost Cooling System

  • Radiator upgrade – Choose a larger 3-core radiator with more cooling fins.
  • Synthetic coolant – Handles higher temperatures with less pressure.
  • Coolant filter – Removes sediment that can cause hot spots.
  • Fan clutch – Firm engagement at lower temps for maximum airflow.
  • EGR delete – Reduces exhaust gas heat load on the cooling system.

Keep engine temps under control when towing in hot weather or up long grades.

Gauge Monitoring

  • Pyrometer – Monitors EGTs to avoid exceeding limits when towing.
  • Transmission temp – Prevents overheating.
  • Boost – Ensures turbo is within safe operating range.
  • Fuel pressure – Spots problems before they cause power loss.

Gauges allow you to monitor vital parameters and adjust driving habits accordingly.

Tires and Suspension

  • LT tires – Load Range E or higher for carrying capacity.
  • Tire inflation – Max pressure for load, but not beyond rating.
  • Shocks – Control bounce and sway for stable handling.
  • Sway control – Reduces lateral movement when dealing with passing trucks or wind gusts.

Prevent blowouts and improve control when running near max towing weights.

Safety Equipment

  • Brake controller – Proper calibration and settings for trailer brakes.
  • Hitch – Rating matched to max towing capacity. Proper setup.
  • Safety chains – Secured properly with adequate ratings.
  • Wiring – Heavy duty harness with adequate capacity.
  • Load balancing – Even weight distribution for stability and handling.

Don’t overlook critical components that affect safety when towing heavy loads.

Gain Experience Gradually

  • Start with smaller trailers and work your way up in capacity as you get practice.
  • Add weight slowly to learn how the rig handles.
  • Get to know your setup on local roads before long trips.
  • Monitor engine vitals and watch for signs of overload.
  • Know your limits and don’t exceed them.

Build confidence with your truck and trailer combination over time. Don’t exceed your experience level.

Real World Towing Capacity

The 5.9 Cummins equipped Rams have impressive tow ratings:

  • 12 valve automatic trucks are rated up to 12,000 lbs.
  • 24 valve autos can tow 13,000-15,500 lbs depending on configuration.
  • Common rail models extend max capacities up to 17,000 lbs.

But real world capacities depend on your setup, mods, and towing environment:

  • Well-maintained truck – Fix any issues that affect power, handling, or safety.
  • Performance modifications – Carefully matched to increase torque and durability.
  • Ideal conditions – Flat roads, good weather, no high altitude or extreme heat.
  • Conservative loads – Leave a 15-20% safety margin on capacity limits.
  • Proper gearing – Put the engine RPMs in the optimal power band.

With the right setup, you can achieve:

  • 12-13,000 lbs with a 12 valve Cummins.
  • 14-16,000 lbs with a 24 valve engine.
  • 17-19,000 lbs with a common rail diesel.

But realistically, it’s best to stay under 15,000 lbs even with a well-built truck. Towing much beyond factory ratings greatly increases stress and wear.

Max Towing Practices

Follow these best practices for safe operation near max towing loads:

  • Thoroughly check truck and trailer before each trip – tires, hitch, electrical, fluids.
  • Keep speeds under 65 mph to reduce strain and improve stability.
  • Allow extra distance for braking.
  • Avoid sudden acceleration and braking which can cause sway.
  • Lock the torque converter and use exhaust braking on downgrades.
  • Shift the transmission manually to control gearing and engine RPMs.
  • Monitor gauges closely for any sign of overheating or overload.
  • Take extra precautions in windy conditions.
  • Balance the load properly and secure cargo.
  • Get to know your rig’s handling characteristics gradually. Start small.
  • Keep the tank over half full to minimize fuel surge issues.
  • Focus on driving and allow extra following distance.
  • Pull over and let the truck cool if needed. Take a break on long climbs.
  • Back off the throttle if the pyrometer reads above 1400°F.

Safe towing requires both a capable truck as well as smart driving habits. Don’t push beyond your experience level.

Is it Worth Exceeding Tow Ratings?

The 5.9 Cummins is a highly capable towing engine. But exceeding manufacturer towing ratings too far can lead to issues:

  • Overheating – can cause engine and transmission damage.
  • Premature wear – to u-joints, wheel bearings, suspension, drivetrain.
  • Reduced braking capacity – increased stopping distance.
  • Handling difficulties – sway, bounce, reduced stability at speed.
  • Higher risk of mechanical breakdowns – leaves you stranded roadside.

Carefully built and upgraded trucks can safely tow near capacity limits. But it’s generally not recommended to exceed by


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