Installing Toyota’s Electric Locker into a 1st Generation 4Runner
http://carterswebsite.com/4runner/mods/locker/ <~Clickit!
(from website)
Drilling & taping
This was the most difficult part for me. It took a couple of tries to get it right. I’d definitely recommend a drill press. I didn’t have one at first, so I tried to use a hand-held drill.
My first attempt ended up with studs that were slightly off-center and not quite perpendicular to the gasket ring. If they are even slightly off, the carrier will not fit snugly against the gasket ring. Therefore, you need a way to mark the exact center of the stud holes so you can drill in the proper place.
Here is what worked for me: I installed the carrier assembly and bolted it down using the 8 existingstuds that fit it. I removed the electric actuator assembly to gain some more clearance. If you do this, be careful not to move the actuator arm inside the differential while it is separated from the electric motor.
Next, I found a drill bit that is almost exactly the same diameter as the inner-diameter of the stud holes in the carrier (22/64" I believe). Using this larger bit, I drilled straight down through the stud holes to mark the gasket ring. I drilled down until the larger drill bit had made a crater in the gasket ring so that it would help guide the smaller drill bit I actually used to drill the hole.
Once the center positions of all four of the new stud holes were marked in this fashion, I used the 17/64" drill bit to drill the holes. Don’t do this! There are two problems here. First, I counted on the 4" long stud hole to keep the drill bit perpendicular to the gasket ring, but since the 17/64" is considerably smaller than the stud hole, it ended up drilling at an angle, so the stud was not perpendicular to the gasket ring. Second, the 17/64" drill was large enough to "walk" in the crater I drilled with the larger drill bit and so it still ended up slightly off center. In the end, I had to hog-out the lower part of one of the long stud holes in the carrier to a larger diameter.
To avoid these problems, I suggest that you remove the carrier after marking the center of where the stud needs to go with the large drill bit. Then, use a small drill bit to drill a pilot hole. Use a drill press to do this and make sure that you get it perfectly perpendicular to the gasket ring. Once you get a pilot hole drilled, drill it out to 17/64".
Once you have drilled the new stud holes, use a 8mm x 1.25 and tap some threads in them.
You do not need to do anything to the unused stud holes.
Here are a couple of pictures showing the modifications (click on images to view larger version):
