4x4 AnswerMan: LSD & Lockers, Overheating Engines, LED Headlights and More

We dive into your questions

Jul. 18, 2017 By Jaime Hernandez

Have a truck, Jeep or SUV question for the 4x4 AnswerMan? Send your questions to [email protected] Please include your name and location, and be as detailed as possible about your questions.

Previous 4x4 AnswerMan Columns

May/June 2017 - AWD vs. 4WD, Shifter Repair and More!

April 2017  - Turbocharged Gas Engines, Off-Road Training and More!

March 2017 - How to Repair a Flat Tire, Off-Road Van Conversions and More!


Differential Traction: LSD & LOCKERS


  Dear 4x4 Answerman,

What is the best option for off-road differentials? Been looking at what's available and I'm totally confused.


If you've ever gotten stuck off-road due to wheel spin, chances are power was only going to a single wheel on the axle, not both.  It probably was also the wheel digging into the ground or up in the air--not the one sitting flat on the ground that could have helped propel you forward.  The culprit: an open differential (a.k.a. Peg-leg).

 Shown here is an Eaton E-Locker designed to lock the differential.  It can be engage/disengaged with the flip of a switch using 12V power.

Since most vehicles come with open differentials from the factory, adding a differential traction aid will help deliver power to both wheels on the axle—making for better off-road performance.  Limited Slip Differentials (LSD) and Lockers are the most popular.  In fact, they are so popular that many new vehicles with “Off-Road” packages are now offered with one of these traction devices from the factory. 

Limited Slip Differential (LSD)

A Limited Slip Differential adds traction by sending power to both wheels and prevents excessive power from going to only one wheel.  The Eaton Posi limited-slip differential, for example, prevents wheel slip by using carbon disc clutch packs preloaded by a central spring assembly located behind each differential side gear. When torque input increases, the clamping load on the clutch packs increases.  This causes the clutch packs to grab and transfer power to the other wheel.  LSD is a good choice for vehicles driven on both street and dirt.

Differential Locker

The Differential Locker is designed to send equal power to both left and right wheels on the axle.  This level of traction is awesome off-road, but not very street friendly when locked.  Going around corners will make the tires bark since each wheel can't spin independently.  It also wears tires fast.  Some mechanical lockers, like the Detroit Locker, get around this by allowing the wheels to spin at different rates when going around corners.

If you want the best of both worlds, a Selectable Locker gives the driver more control by allowing the differential to be locked or unlocked with the push of a button.  Selectable lockers use either electric or air actuators to engage and disengage the locking mechanism inside the locker, sending power to both wheels.  They can be installed in front or rear axles and are a good choice for vehicles that see heavy off-road use.
Both LSDs and Lockers are good options for adding traction to your vehicle off-road.  In most cases, the Limited Slip Differential is more than enough.  But if you find yourself rock crawling or tackling technical terrain, a locker may be a better choice.

Now go get more traction!


LED Headlight Flicker

4x4 AnswerMan,

I just installed aftermarket LED headlights on my RAM.  The lighting power is awesome, but sometimes they flicker.  Any idea on how to fix it?  I was told the problem might be in the wiring?


Hey Frank,

Sounds like it might be the CAN-bus causing the LEDs to flicker.  This is a common issue with Chrysler vehicles, including Dodge, RAM, and Jeep. If your vehicle came originally equipped with Halogen headlights, you may experience light flickering when replaced with an aftermarket HID or LED headlight.

The easiest way to fix this problem is by adding a CAN-bus anti-flicker module. It installs inline between the headlight plug and factory wiring.  The CAN-bus anti-flicker module helps regulate power delivery to the new headlights.  If you don't run an anti-flicker module, not only will your headlights go haywire, they may even throw an error code/check engine light on the dash.



Josh Burns has been hard at work this year turning a Lexus GX 470 SUV into a more capable off-road vehicle.   There were some skeptics that balked at the idea of turning a luxury SUV into an overland rig, but Burns made it happen.  Several key off-road upgrades including suspension, wheels/tires, and body armor helped turn this GX sports utility vehicle into a bona fide 4x4 trail rig ready for adventure.

You can check out the build by clicking on the stories below:

Luxury Off-Road: Why We're Building a Lexus GX 470

Icon Vehicle Dynamics, Metal Tech 4x4 GX 470 Rear Suspension Install

GX 470: Metal Tech 4x4 Swing-Out Bumper Install


Hot Radiator

4x4 AnswerMan,

My truck keeps overheating whenever I go off-road.
Will an aluminum radiator help?


Hi Ron,

Sorry to hear things are getting hot on the trail.  An aluminum radiator may help keep overheating problems at bay, but before you go spend money on a sexy radiator, lets make sure some of the fundamental engine cooling components are in good working order.

Check the radiator fluid. If there's rust or debris in there, you need to have it flushed. Clogged radiator veins don't do much for cooling power. 

You also want to check the thermostat. Sometimes they will stick and will cause the vehicle to overheat because it's not getting any coolant flowing from the radiator to the engine. You may be able to diagnose this with an OBD-II Scanner (if there is a sensor for the thermostat). Look for a P0128 trouble code. For older vehicles that don't have thermostat sensors, you will need to physically remove and inspect the thermostat to confirm it is working properly and not sticking. 

Another item to check is the fan clutch. With most off-road travel being done at lower speeds, low RPMs can lead to poor cooling, especially if the fan clutch isn't working properly. With the engine off, the fan clutch can be checked manually. You should be able to spin the fan and feel some resistance. If it spins with no resistance at all, it probably needs to be serviced or replaced.

While you're at it, also check for cracked hoses or any leaks. If everything checks out, you may need to make some engine cooling upgrades for off-road use.  An aluminum radiator will help the engine run cooler. Another mod is to add an electric fan. This will help dramatically at slower speeds and on the trail since it increase the airflow.
Stay cool!



4x4 AnswerMan,

I just got a Jeep Wrangler and wanted to know if I need new shocks.  It has just over 75,000 miles on the odometer.  My buddy says they need to be changed every 50,000 miles, but they seem fine.  Do I need to buy new shocks?

St. Paul, MN


Hi Jerry,

Your friend is partially right.  Shock absorbers are wear parts, so they do need to be replaced eventually.  There are a few shock companies that recommend replacing them at 50,000 miles, but we've found this isn't always the case. The life of a shock really depends on driving style, quality of shock and vehicle maintenance history. For example, some monotube gas pressured shocks can go well over 100,000 miles with no problems.

What you need to do is take a closer look at the brand of shocks you have installed on the Wrangler. After you know what they are, you can find out from the manufacturer what they recommend for service and replacement.

Good luck!


Heavy Load Range Tire

Hi 4x4 AnwerMan,

I'm looking to upgrade the stock tires on my Ford Super Duty diesel to an all-terrain.  I like the factory 18-inch wheel, but am having trouble finding a tire that matches the factory Load Range in an all-terrain.  This is a deal breaker since I tow a 5th wheel and would like the piece of mind or a higher load range rating.  Do you have any recommendations?

Tempe, AZ


Hi Tim,

Toyo Tires has an F-Load Range tire they recently launched that might be a good fit.  The F-Load Range tires allow for higher carrying capacity at a higher inflation pressure compared to tires of the same size with an E-load range.  They are available in mud terrain and all-terrain thread patterns for 18-, 20-, and 22-inch wheels from 33-inch diameter all the way up to 37s. Make sure to check out Toyo Tires for more info.

Have a truck, Jeep or SUV question for the 4x4 AnswerMan? Send your questions to [email protected]. Please include your name and location, and be as detailed as possible about your questions.


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