3rd Gen 4Runner E-locker Retrofit
By: Bob_98SR5
Date: August 27, 2007

Parts List
Toyota E-locker
4.56 ratio -> #41110-3D010
4.30 ratio -> #41110-3D080
4.10 ratio -> #41110-3D030

Permatex Grey RTV Sealant
OEM locker differential gasket (#42181-60050---use it for a template only)
111mm differential studs- #90116-08330 (2)
Diff. Lock ECU #89533-35070
Diff. Wiring Harness #82127-35100
Differential Switch (stock Toyota switch is #84725-35010)

Tools and Supplies
Socket and combo wrench set
24mm (12 point) socket
Tire jack and stands
Racheting straps (2)
White grease pen or Black Sharpie
Plastic baggies and twist ties
Fluid drain pan
PB Blaster
Deburring tool

Electrical Kit
Soldering gun and wire
Wire stripper
Electrical tape
Red connectors
14-16 gauge wire (assorted colors)

Brake Bleeding Kit
One-man Bleeder
Brake fluid (three 16oz bottles)
2 x 4 (6” long)

Retrofitting a Toyota e-locker (or any locker, for that matter) is one of the most talked about modifications that seems to be out of reach for many Toyota off roaders for many reasons. For starters, there are cost considerations. A used e-locker (3rd) may cost up to $600, depending on the source. Another factor is time and expertise to retrofit it. Fortunately for me, I was able to purchase my e-locker for around $250 and had some help from UltimateYota.com members for the install. In addition, there is a wealth of information online as well as prior writeups on this modification (links at the bottom of this writeup). Thus, I give credit to those prior authors of e-locker retrofits who are listed at the bottom of this writeup.

Note: the writeup is based on removing the entire rear axle and not just the differential---there's a lot of parts that do not have to be removed if just replacing the differential. And unlike my other writeups, pictures are a little sparse in this writeup because the work was pretty dirty and intensive---grabbing the camera and writing down stuff was the last thing on my mind. With that, read on!

Step 1: Spray PB Blaster on Everything!
Especially for you East Coast guys, spray the hell out of everything with PB Blaster that looks like a nut, bolt, etc. near the rear axle. That also includes the hardware on the brake backing plate and the rear driveshaft nuts. I don't have the time or patience to name each and every one, but if you read this writeup to the end, you'll have a very good idea of what needs to be sprayed.

Step 2: Draining the Rear Differential Fluild, Removing the Rear Tires and Securing the Axle
While your vehicle is still on the ground, use a 21mm deep socket and a cheater bar to loosen up the lug nuts on each rear tire. Next, pull your e-brake, chock your front tires, and jack up your vehicle. Set the jack stands on the rear frame rails and bring your vehicle slowly down on your jack stands. On the rear of the differential, unbolt the 12mm rear brake cable bolt. This will allow you to maneuver your 24mm socket (use a 12 point) on the ½ inch socket wrench onto the top 24mm (fill) bolt. Turn it counterclockwise to remove the plug. After removing this plug, remove the bottom 24mm drain plug. Allow it to drain out.

Loosen the lug nuts, lift and remove the tire   Drain out the differential fluid. Pull the fill plug first!

Also, if you have bungees or straps, now is a good time to wrap the axle to the frame to prevent it from crashing down when you remove the axle.

Step 3: Unbolting the Driveshaft
There are four bolts held by 4 nuts that connect the driveshaft to the front of the 3rd member. Using two box wrenches, remove the nuts from the bolts and store in a safe place. If you have racheting wrenches, this is one of those times where it pays for itself! Luckily, Lance had some and it made the job a lot easier. If you can pull off the driveshaft or if it naturally falls off, then great. But we had to give the 3rd member a nice little whack with a rubber mallet to get it off. The driveshaft is heavy and may come down with a thud, so be careful.

Step 4: Unhooking the Brake Lines
Use a 10mm wrench to unhook your brake line connections. There will be some residual brake fluid loss, so have your baggie and zip tie handy Using a 10mm socket wrench, undo the two brake line to the T-connector at the top of the rear differential:

Unbolt brake line (B)   Unbolt brake line nut on both sides

As your brake fluid begins to weep out, back off those center lines from the T-connector and then zip tie the baggie as shown below. Notice the amount of fluid in the baggie:

Here's a shot of both lines unbolted   Baggie it to catch the brake fluid

Similarly, there is a single brake line going into the rear drum backing plate. Undo that line and put a baggie over it. Next, pull out the ABS connector (if you have one) from the hole as pictured below:

Unplug the ABS sensor   Here's a shot of the ABS sensor removedd

Lastly, loosen the four nuts that secure the rear drums to the axle shaft. We'll be taking off the drums later. Remember to always to keep the hardware attached and/or well accounted for during this writeup. There's gonna be more nuts lying around than Paris Hilton can handle in one night in this writeup.

Step 5: Removing the Sway Bar and Panhard Drop Bar
Begin by removing the top nut on the sway bar end link. You may need to use a crescent wrench to prevent the sway bar from over-twisting as you unbolt it. After unbolting the end links, pull the end links out of the mounting hole and lightly reattach the end link parts, so you don’t forget the order (like I did). Next, there are 2 sets (total of 4) of sway bar bolts that are attached to the rear axle. Use a 12mm socket wrench to remove these bolts. Finish by removing the sway bar from the driver’s side to the passenger side and put it aside with the 4 bolts.

Unbolt the top nut (E)   Unbolt sway bar nuts (S) on both ends, lower shock bolt (B) and LCA nut (L)

Step 6: Removing the Shocks, Lower Control Arm

You will need to unbolt the lower shock bolt with a 17mm box wrench as pictured above. Remove the lower control arm bolt using a 19mm box wrench. Unbolt only one of the the panhard drop bar bolts (driver's side) with a 17mm box wrench.

Unfasten the panhard bar nut

Lance showed me a great trick to removing the LCA bolt by using two wrenches together to lever off the panhard bolt:

You are now ready to remove your rear axle shaft.

Step 7: Removing Springs
At this point, all you need to do is to press down on one end and pull out your springs. Repeat for the other side.

Step 8: Removing the Axle Shafts
This is a job best done with a friend. With one person grabbing and pulling the axle shaft out, the other person should be making sure that the end of the axle shaft does not scratch or gouge the inner shaft wall itself. Pull out the axle shaft and place the drum end on a towel or cardboard box. The shaft should be pointing upwards to the sky so as to avoid any damage or dirt from contaminating the splines. If you want to be extra careful, wrap a baggie around the end of the splines.

Yes, it does balance on its own

This is an excellent time to examine your rear axle seals. If they require replacement, now is a good time as any to replace them. And even if you don’t, you got everything undone to place a fresh set of seals in! See my rear axle outer seal writeup here (pending).

Step 9: Modifying the Rear Axle Housing
Now since I purchased a spare axle housing, I worked on that one instead of the one that came from my vehicle. However for the sake of the writeup, I will describe the procedure from the standpoint of everyone else. The first step was to remove the bungees or jackstands that are holding up your axle. Work with a friend to gently lay it down and pull it out from underneath your 4Runner.

There it is in all its glory

The first thing you want to do is to take your gasket and place it on your bare rear axle you just pulled out. ***Carefully*** mark the center of the holes you need to tap. Tip: tape the gasket down, so it does not move!. In addition, you will also see a C-shaped notch that accomodates the e-locker shift fork itself as well as a smaller one located up top. Cut those portions out. For the long studs, use your welder to create a little material for the 3rd member for the e-locker to sit on:

Drilll out holes (H), cut notches (N), and drill out long studs (L)

When I first tried to drill and tap holes just as the picture shows above, I really screwed it up. Robinhood4x4 suggested a better method which worked. Place your axle on jackstands, wood frame, etc. to make sure the axle is level and secure. Next, bolt on your new e-locker differential to your axle housing simply by securing it down with the existing nuts onto the axle housing's bolts. By doing so, you will see which holes need to actually be tapped and best of all, the e-locker differential's holes act as a guide for your drill bit to perfectly create new holes. Also, if you have a friend around, have him make sure your drilling is perpendicular to the axle's face while you are drilling the holes.

Remember, tapping new holes takes great patience and the right technique. Make sure for your first few threads, back out the bit about a 1/4 turn to allow the tapped metal material to make its way up the tapping bit's flutes. As you go further down, you do not have to back out the bit as often.

After tapping the new holes, secure the new double threaded bolts into the new holes. For the area near the taller bolts, add a bead of weld off to the right of these tall bolts and grind them down flush w/ the rest of the axle seal's surface. This will provide the extra surface area needed for a good seal.

Next, clean up the inside of the housing very thoroughly with brake cleaner as well as compressed air. Secure the 3rd member onto the bare axle with Grey RTV sealant.

A note on gaskets vs Grey RTV: The Toyota gasket did not work for me at all and I am not the only one who experienced the same misfortune. This pictures shows me applying Grey RTV because the gasket leaked. I had to unbolt the driveshaft, back out the 3rd member, carefully tear out the old gasket, and then awkwardly apply Grey RTV. Fortunately, the Grey RTV worked.

Step 10: Wiring the Locker Using an Aftermarket Switch
Fortunately, there are many options for wiring a switch to your e-locker---each method has its pros and cons. I will not discuss them here. The first choice is the standard Toyota e-locker switch. Also, Inchworm makes a kit as show here. A third option is from Downey, a cable actuated system as shown here. Finally, there's the make-it-yourself option. Robinhood was kind enough to make a two relay system for me and it works just fine. Here are the diagrams of the one Steve based the control system he made for me here. It is located at the bottom of the page.

Once you've decided on your switch option, you will need to wire the locker to your switch and then to your power source.

Step 11: Routing the Harness
You will need to use your wire harness, plug it into the e-locker motor, and attach it to the e-locker harness bracket. At this point, you will need to solder quite a bit of wire to run the wires to the front. I suggest you measure the distance and add another 50% just in case. After soldering new wires to your wiring harness, I highly suggest you wrap them tightly with electrical tape or shrink tubing. Run the harness towards the front of your vehicle and underneath on the driver's side and run them through the hole under the passenger seat:

Run your wires underneath the step plates towards your firewall and through it. Route the wires to your power source (mine is an auxiliary fuse box, but you should normally use a switched 12volt source) and then to your relays or control ECU. In my case, Steve made a two relay system with a switch. I ran the appropriate wires to the relays and a few to the switch itself:

Step 12: Brake Bleeding and Rear Differential Fluid
Don't just take off yet! Make sure you refill your brake fluid system as well as the rear differential. My writeups on these two topics will be posted in the near future.

Step 13: Testing and Operation
A locker can be used in many ways in many situations, but remember that an engaged locker is not to be used on sharp or even mild turns on pavement. If you are going to test the locker on pavement, make sure you test it going slow and in a straight line. You may find that the locker does not engage right away. Don't worry, I've read that it happened to alot of people, including me.

To disengage your locker, turn it off and put it in 1st gear. Gently rock the wheel and move forward. You should hear a very distinct click, which is your gears returning normally to its open differential configuration.


This is by far the most involved and complicated mechanical procedure I've done to my truck. Also, please refer to these e-locker retrofit writeups. They were immensely helpful:


Questions or feedback? Email me and I'll try to get back to you. If this article helped you save time, money or just made things more convenient for you, please consider donating to keep this site alive.