Everyone who has wheeled an open diff vehicle at one time or another knows the feeling. Youre halfway up a rutted hill or off-camber ledge. Youve got the transfer case in low range and you can feel the torque of the engine through your seat. The suspension groans as it follows every crack and dip in the terrain keeping the tires in contact with the ground. Then, just when you start getting that cocky feeling that youre going to make it and that your rig really is the bombdespite what your friends with their modified rigs saythe engine rpm comes up. You stop going forward and quickly slide back about a foot or so as the tires kick up clouds of dirt from opposite ends of the vehicle. You just reached your potential and nothing but more momentum, greater articulation, or a traction- aiding device will take you farther.
Total thrash trail beaters usually leak oil, get crappy mileage, shake on the highway, and have rear spools or auto lockers that chirp tires going around corners or when parking. Were all for driving them everywhere every day, but we know thats just not usually the case for most of you. And it wasnt the case for our 85 4Runner. Our goal with this vehicle is to develop it into a well-balanced machine that can carry the crew to Vegas for a weekend, cruise through the Rubicon without difficulty, or even trek across the country in comfort while getting respectable mileage.
We wanted lockers, we wanted to increase the gear ratio from 4.10 to 4.88 for better acceleration, highway cruising capabilities, and off-road performance, and we wanted to upgrade our spindly four-cylinder Toyota centersections to the beefier six-cylinder versions. Also, since Toyota axles have a drop-out third member just like a Ford 9-inch, we wanted to order the gears and lockers set up in the new centersections so we could install them ourselves in the driveway the day they arrived.
Since we feel that limited slips belong in cars and automatic lockers or spools were too harsh for a vehicle that the wife would occasionally drive (yes, we realize this isnt the case with every wife), a pair of ARB air lockers was the natural choice. For the uninformed, an ARB air locker is a pneumatically actuated locker that operates as an open differential when not engaged, but that locks both axleshafts together just like a spool when engaged. That means you get tractorlike grip in the dirt with none of the drawbacks of an automatic locker or spool on the street.
We contacted Gary McFadyen at West Coast Differentials for all of the parts wed need. West Coast Differentials carries just about every part made for every axle, so filling our order was no big deal. McFadyen had his boys assemble a pair of V-6 centersections with quality Sierra Gear ring-and-pinions on the ARBs. Since Toyotas use a crush collar on the pinion, West Coast Diffs also included driveshaft flanges so we needed to let them know our driveshaft type. West Coast Diffs also shipped us an ARB air compressor. Theres nothing worse than hunting down parts so we really appreciate companies where we can one-stop shop.
We had reservations going to 4.88s from the 4.10s with only 32-inch tires, but it turned out to be the right choice. The first thing that was noticeable was how quickly we needed to get into Second gear. The little 22RE four-cylinder spools up quicker than before and feels a lot more brisk when pulling away from stoplights. The desire to reach through the firewall to strangle the wheezing squirrel isnt there anymore. On the highway, we can now pull grades in Fourth or Fifth that used to require a downshift to Third or Fourth. Were also finding ourselves driving with our foot off of the floorboard, where before wed just mat the gas and wait for acceleration that never came.
Off road its night and day. No matter how many times we experience it, it always amazes us what a total transformation a locker can make in an off-road-driven vehicle. We find ourselves using the rear locker for most situations and engaging the front one only when necessary. We guess were a little gun-shy after seeing so many busted Birfield joints. Where we once had to hit nachos and rutted hillclimbs with speed and lots of throttle, we can now just elegantly creep up and over.
Another added benefit is the ability to drive in sand. Wed really need to let the poor four-cylinder have it with the open diffs, but now with all four tires contributing were able to make it to the top of dunes that used to totally spank us with less throttle. All in all, the lockers are probably the single biggest improvement to this vehicles off-road prowess that well be able to make.
West Coast Diffs did an awesome job setting up the gears and plumbing the air lines. The gears run quiet and cool and when the lockers are engaged there are no annoying air leaks to set off the compressor every five seconds like weve seen with some inferior installations.
The rear diff installation is cake. For each side you simply unthread and cap off the brake line, disconnect the parking brake cable, and remove the four retaining nuts. The axle/drum assembly can then be slid out enough to clear the carrier.