The hubs are in the center of your front wheels. These hubs on the 90 and newer 4 wheel drive 4Runners are automatic and have a Toyota center cap on them to match the rear wheels. The auto hubs can be removed and manual ones installed. You can use hubs from an older 4Runner/pick up or a set of aftermarket hubs such as Warn.
It will take a few hours to install them and cost about $100 for the hubs.
They are not "Automatic" they are LOCKED! Toyota wanted to market the truck as "shift on the fly" and not pay AISIN for their hubs. :wtf:
Find a pair of IFS hubs, buy new gaskets, o-rings, & cone washers (optional) from the dealer, get rid of the garbage Toyota gave us and enjoy ~3mpg increase in mileage, & a better driving truck.
If you clean & paint the new hubs, study the manual, & plan ahead it's 30 min swap. The only tricky part is removing the cone washers. If you're lucky you won't even need to remove the wheels.
Make sure you have a brass punch, & BIG hammer. You can beat the hub body to break the cones loose, but you risk more than you gain, buy the punch! It helps to soak the cone washers in PB Blaster, & relax. The parts from the dealer will cost you ~$20.00 (if you spring for the new silver cover bolts), 8 bucks if you don't.
I've done this on 4 trucks/runners over the past 25yrs. You won't regret spending the time/money.
Bob
Check out this link if you don't want to rebuild the hubs yourself.
http://www.wabfab.org/aisinmanualhubs/aisin.htm
BTW, if you want "shift on the fly" just lock the AISIN hubs!