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How to install a BD 2 Low Unlock kit in Ram 3500

Unbound Glory

Bruce W. Smith
Mar 10, 2017
Photographers: Bruce W. Smith
Towing heavy trailers with four-wheel-drive trucks has its advantages, most notably the added traction provided by the front differential and the ability to drop the transmission into low range when certain conditions require slower speed. The latter becomes a huge advantage for 4x4s with manual transmissions, where backing up or easing around a corner in “4Hi” is a sure way to smoke a clutch.
The downside of using “4Lo,” regardless of whether the transmission is a manual or automatic, is that when the front axle engages, the power transferred to the driver side tends to place that tire in a bind when the steering is at full lock, causing it to start hopping or scuffing as the tire is trying to move the load and turn at the same time. This is very noticeable when trying to maneuver a long, heavy trailer in tight quarters.
Photo 2/17   |   Bd 2 Low Unlock
Owners of trucks with manual-locking hubs can simply keep the front hubs unlocked to avoid such issues. But for those people who drive four-wheel-drive rigs that have automatic-locking hubs and electronically activated four-wheel-drive systems, getting into “2Lo” isn’t quite as simple. Somehow, the switching mechanism that engages the front axle when the system is switched to four-wheel-drive mode must be bypassed.
That’s precisely what BD Diesel Performance’s engineers have done with their elegantly designed 2Low Unlock Differential Kit ($156.00). The system tees into a truck’s four-wheel-drive control module and features a driver-activated switch that enables/disables the solenoid for the axle-locking mechanism inside the front differential. When the 2Low Unlock is turned “On,” prior to switching the truck’s four-wheel-drive selector into four-wheel drive, the front axles are disengaged. When the switch is left “Off,” the four-wheel drive system functions normally.
The device takes less than two hours to install, as we learned while watching Mobile Diesel Service’s Mat Johnson set up the unit in a customer’s ’14 Ram 3500. The Ram is used for towing heavy gooseneck equipment trailers during the week and a big toy hauler for weekend play. Most of the time, the owner works with loaded trailers in close quarters while making full-lock turning maneuvers in 4Lo, which always leads to the front wheels scuffing and hopping. BD’s kit quickly solved those issues.
Photo 3/17   |   A simple push of this dime-sized rocker switch allows drivers of four-wheel-drive ’09-to-’17 Ram 1500, ’14-to-’17 Ram 2500, and ’13-to-’17 Ram 3500 models to use the trucks’ low-range transfer case without engaging the front axles.
Photo 4/17   |   BD Diesel Performance’s 2Low Unlock Differential Kit ($156.00) is a simple plug-and-play wiring harness with a lighted rocker switch. Installation takes about two hours, depending on application, and it’s all done inside a truck’s cab.
Photo 5/17   |   On our ’14 Ram 3500, the four-wheel-drive control module is located on the passenger side, high on the floor behind a small box with a snap-off plastic cover.
Photo 6/17   |   This is the control module that sends a signal to the front differential to engage the front axle when the four-wheel drive mode is selected. BD’s wiring harness taps into the module at the blue connector.
Photo 7/17   |   Mobile Diesel Service technician Mat Johnson unplugs the blue stock connector and plugs the prewired 2Low Unlock harness in its place. It doesn’t matter which of the two plugs on the BD harness are used.
Photo 8/17   |   The other blue connector on the harness mates with the stock plug that was disconnected, effectively establishing the tee-style union of the truck’s four-wheel-drive and BD’s 2Low Unlock systems.
Photo 9/17   |   After the BD device is plugged in, Mat uses plastic ties to secure the wiring harness.
Photo 10/17   |   The four-wheel-drive control module’s protective plastic cover is trimmed to fit over the added bulk of the 2Low Unlock’s connectors and wiring harness. Straight-cut snips make easy work of this process.
Photo 11/17   |   When finished, Mat’s handiwork almost makes the module and cover appear as though they came from the factory that way.
Photo 12/17   |   The plastic trim under the steering wheel and the center stack’s lower fascia are popped free to run the wiring harness from the control module to the 2Low Unlock’s activation switch. Mat runs the wiring just under the lower edge of the console, hiding it from view when the fascia is reinstalled.
Photo 13/17   |   Newer Ram trucks have sealed electronic modules placed behind the center stack, making it very difficult to install a switch anywhere in that area. Our truck doesn’t have auxiliary switches, either. So we’re placing the 2Low Unlock’s activation switch next to the ignition key, which makes it both easy to install and to use.
Photo 14/17   |   A step-bit is handy for drilling a ¾-inch hole through the steering column’s lower fascia, making way for the BD-supplied activation switch.
Photo 15/17   |   Wiring the rocker switch is simple. Three leads in the 2Low Unlock’s harness plug into the switch: blue (top), pink (middle), and red (bottom). Power is supplied through the truck’s four-wheel-drive control module, so no other wiring is needed.
Photo 16/17   |   A little of the plastic by the ignition switch must be trimmed away so the cover under the steering column fits back into place.
Photo 17/17   |   When the cover is reinstalled, the 2Low Unlock activation switch looks right at home next to the big Ram’s ignition switch. This device makes a huge difference when it’s engaged, allowing full-lock steering in low range, without any hopping or binding of the front tires.

Sources

BD Diesel Performance
Sumas, WA 98295
800-887-5030
www.dieselperformance.com
Mobile Diesel Service
541-459-8939
mobilediesel.co

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