The question of retrofitting oem Toyota electric differential lockers to non-lockered axles come up quite a bit. On this page we would like to point out some of the things that need to be done. Yes, it can be done. Typically at shop rates, it is not cost effective. It doesn't mean it can't be done.
By far the easiest and cheapest way to do it, is to find donor axles from a truck to just swap into yours. You will also need the diff lock ecu, and various pieces or the electrical harness. If you locate a truck of the same vintage (ie, 1993-1004 or 1995-1997) it should be a simple plug and play option.
The harness from the switch position (to the left of the steering wheel) to the ecu position (in the right kick panel) is already installed. What is needed is rear harness from inside the left side rear quarter panel to the locker and the front harness. As well as the locker ecu.
Although the axles from all the years should interchange, the harnesses does not. You would also have to put the lights & sockets into the instrument cluster to make it light up.
If complete axle housings with third members are not available, then you can retrofit the third member. This ranks high on the banana scale, and should not be attempted without the right tools and knowledge.
Below is a photo of a front housing, showing the new holes that need to be drilled and the area that needs to be notched. As can be seen from the photo, it can be done, however the seal area is quite a bit smaller and can cause leaks in the future.
We will expand on this page as soon as we have more pictures available.
Front housing modified to accept electric locker third member
More information from James Chow
I noticed the skeleton writeup on the sleeoffroad page on installing factory elockers in non-locking diffs. I had done this in Jan to my 86 4-cyl 4Runner. I know a number of sources sell the 8" toyota hi-pinion diff w/ locker for the front for about $800 (rear 8" diff is the same price; haven't seen a price for the 9.5" diff, though). Anyways, since my rig has a 4 cyl axle housing, one has to not only grind out the large notch for the actuator motor as you have shown on your site (my fab guy used a sawzall, then grinder; some guys use a plasma cutter or just grind), but also notches for a thicker (V6) ring gear. The two holes that are too close to the edge of the gasket lip can be remedied...one simply welds a bead, then grinds it down, then drills the holes and taps them and threads the two longer studs in for the actuator. A number of people on the Toyota 4x4 sites have retrofitted their diffs w/ factory e-lockers. In my case, I had a fab shop (Inchworm Gear) make the axle housing mods (they charged $225) while I built my own ECU using Mike Carter's design that uses two SPDT relays (link below). I used the toyota harness from the diff (has a breather for the actuator that should be extended, but I just attached it to the bottom of the bed), cut off the connector, then soldered on 6 conductor wire that leads up to the relay circuit in the engine compartment at the firewall. From there, I run 3 wires into the cab (lock, unlock, and locked light indicator) to a SPDT rocker switch in the dash (OEM switch/location). That switch is controlled by a SPST rocker switch mounted in a location that a passenger can't reach (so he doesn't accidentally switch on the locker at 60mph!). Phorunner's writeup uses the factory ECU (newer 4runner came partially wired), but shows how to defeat the 5mph and 4wd low speed requirements.
Here are some photos of someone else's install: http://www.phorunner.com/e-locker.html
This guy's circuit design has been used my many people, including myself: http://22.214.171.124/carterman/4runner/mods/locker/