There is a new locking differential hitting the States right now, and OFF-ROAD magazine was one of the first to receive TJM’s new Pro Locker—a locking differential that goes from an “open” position to a completely “locked” position using an air-driven actuator. But this isn’t what you think it is. Yes, coincidentally TJM is also an Australian 4x4 products company, but this is a mechanical locker activated by an air-and-spring-operated actuator that uses a fork to push or pull an internal selector ring on the differential, mechanically engaging the lock ring and subsequently locking both axleshafts together. Upon initial inspection, we were impressed by the thick carrier and liked the optional compressor package that came with the Pro Locker. The air compressor, solenoids, wiring, and air lines were all there, and we liked that a hard reinforced rubber air line is supplied to connect to the bulkhead on the axlehousing. From the bulkhead, a copper air line routes down to the air-and-spring-operated actuator. This is where we got a bit excited. Though the Pro Locker works fine out of the box, we started geeking out on the potential for needless modification of the actuator, and for some great trail fixes should the actuator ever lose air pressure somehow. For now, we’re taking an initial inspection of the newest locker to hit the USA. We installed the Pro Locker in a rear Dana 44 axle using a West Coast Differentials 4.10:1 ring-and-pinion set and WCD full installation kit with Timken bearings. We’ll have a long-term update in an upcoming issue of OFF-ROAD after we get some time and abuse…er, use, on it. OR Specs Differential Type: Locking differential with open and locked positions Locking Actuation: Mechanically locking with air-driven actuator Application tried: Standard Dana 44 Axle Spline Count: 30 Carrier Split: 3.73:1 and (numerically) lower / 3.92:1 and (numerically) higher Ring Gear Size: 8.5 inches Estimated Cost: $800 1. The TJM Pro Locker has a one-piece cross shaft and four large pinion gears inside the thick carrier. It works with mechanical movement of the internal selector ring by the fork on the actuator (a separate unit not shown in this diagram). The selector ring engages the locking ring which locks the side gear to the carrier and immobilizes the ability for axleshaft speed differentiation, thus turning the open differential into a fully locked unit. The Pro Locker is available for the Dana 44 and Toyota Tacoma and Land Cruiser axles. Dana 30 and Dana 60 applications are coming.1. The TJM Pro Locker has a one-piece cross shaft and four large pinion gears inside the t 2. The TJM actuator is held in place on a bracket that uses the carrier bearing cap bolts. It has a fork that mechanically moves the internal selector ring and locks the Pro Locker when air pressure is applied in the air lines via a switch on the dash. Upon disengagement, a solenoid releases the air pressure in the line and a spring inside the actuator moves the fork back and opens the differential.2. The TJM actuator is held in place on a bracket that uses the carrier bearing cap bolts. 2. Here we see the potential for needless modification, if one chose to do so. Since the actuator is completely external of the Pro Locker differential itself, it can be modified or even replaced easily, without ever having to remove or dismantle the differential itself. A savvy machinist could make something that works with a vacuum draw instead of positive air pressure, or an electric actuator could be fashioned easily enough, or even a cable-actuated actuating mechanism could be fashioned.2. Here we see the potential for needless modification, if one chose to do so. Since the a 3. We started our install by gutting the axle, and cleaning out the housing. We used a 7/16-inch (15/32 will also work) drill bit to cut the hole in the top of the differential (make sure to locate an appropriate spot that has clearance for all moving parts in the axlehousing). After the hole is drilled, you’ll need to use a 1/4-inch BSP (British Standard Pipe) tap to create the proper threaded hole for the TJM air bulkhead to install into the housing. Do not use 1/4 NPT! It will not work and you’ll disfigure the bulkhead. TJM is thinking of including these taps with the lockers since BSP tap sizes are not readily available at every hardware store across America. We also took this opportunity to mock up how the actuator’s copper air line fits into the bulkhead.3. We started our install by gutting the axle, and cleaning out the housing. We used a 7/1 4. We ordered a TJM Pro Locker for our existing gear ratio of 3.73:1. Of course, soon after that we decided to take the opportunity of a diff change to swap the front and rear axle gear ratios to 4.10:1 since this particular vehicle runs 35-inch tires. We made a call to West Coast Differentials to see what they had in stock, only to find out that the carrier split on a Dana 44 was not the same as a Dana 60 and instead between 3.73 and 3.92. “Not to worry,” they told us. It turns out that WCD has thick gearsets for guys like us who want to run a (numerically) higher gear ratio on a lower carrier. West Coast Diffs got us out two Sierra Gear 4.10:1 ring and pinion sets, along with two install kits to ensure that we didn’t have to try and reuse shims and bearings.4. We ordered a TJM Pro Locker for our existing gear ratio of 3.73:1. Of course, soon afte 5. Since we were working in our own tech center at the new office, we luckily had a hydraulic press available for us to press the Timken bearings from the WCD install kit onto our 4.10 Sierra pinion gear.5. Since we were working in our own tech center at the new office, we luckily had a hydrau 6. The 4.10:1 thick ring gear from Sierra is just that; thick. It’s made to fit the 3.73-and-down (numerically) carriers in Dana 44 axles. Since we ordered a 3.73-and-down Pro Locker, a thick gearset is our only choice to get a lower gear ratio than 3.73:1(numerically higher).6. The 4.10:1 thick ring gear from Sierra is just that; thick. It’s made to fit the 3.73-a 7. There are two backlash rings that TJM supplies, should you need them, that go outside the carrier bearings on the Dana 44 differential (as opposed to shims that typically go in between the carrier bearing and differential). These rings are machineable if they are too thick. Using some type of surface grinding machine, you can adjust the size of these backlash rings, but you should first try removing shims instead of grinding the backlash ring, if necessary.7. There are two backlash rings that TJM supplies, should you need them, that go outside t 8. TJM supplies an air compressor and two high-quality rocker switches to mount on or under your dash. The air compressor will feed the electrically controlled solenoid that will allow air to fill or escape the 6mm nylon air line that leads to the Pro Locker.8. TJM supplies an air compressor and two high-quality rocker switches to mount on or unde 9. Heavy-duty hard rubber line is used out of the axlehousing. This ensures the lower part of the air line (the part not protected running high along the frame rail) is resistant against rocks, branches, and other debris.9. Heavy-duty hard rubber line is used out of the axlehousing. This ensures the lower part 9. The hard rubber line attaches to the 6mm nylon air line using a push-in fitting that secures the air line to the heavy-duty rubber line.9. The hard rubber line attaches to the 6mm nylon air line using a push-in fitting that se 10. Here is the complete Pro Locker and its actuator installed in our Dana 44 axlehousing. TJM suggests flipping the dash-mounted switch and trying the locker to make sure the actuator’s fork has appropriate spacing to the internal selector ring before buttoning everything back up. We’ll have our opinions on this brand new locker for you in an upcoming Long-Term Updates.10. Here is the complete Pro Locker and its actuator installed in our Dana 44 axlehousing. Sources West Coast Differentials 2429 Mercantile Drive Suite A Rancho Cordova CA 95742 800-510-0950 www.differentials.com TJM 888-951-4TJM www.tjmusa.com By Jerrod Jones Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!