Here are some other 100K+ miles maintenance items that I can think of.
Replace O2 sensor(s?). It responds slower with age.
http://www.4x4wire.com/toyota/4Runner/tech/O2_Sensor/Replace engine timing belt and water pump every 90K-100K miles. You risk destroying the engine if you let it go a long time beyond that without replacing it.
http://www.4x4wire.com/toyota/maintenance/timing_belt/Replace fuel filter, which many people replace at 100K since Toyota doesn't say much about this.
Clean the MAF sensor. See link.
http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.htmlOn my 4Runner, the front swaybar frame bushings died after about 120K miles. The stock rubber split and started coming out of the bracket there. Those are located directly underneath the frame rails behind the front wheels.
Spark plug wires are expected to last about 100K miles. Their electrical resistance supposedly increases with age.
Also refer to the 30K mile maintenance schedule which is explained here:
http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/I know many other vehicles recommend getting fuel injectors cleaned at 100K miles. I don't know what Toyota recommends.
To add to Dandeman, common cause of the axle seals popping is because the breather is clogged; the gases have to vent, so when this is clogged, pressure in the tube builds up, and eventually causes the seals to fail.
I agree that that's one of the possible causes, but I disagree that that's the most common cause. My rear axle seals leak and I get the rear axle rebuilt roughly every 50K miles. You're lucky if you haven't had to deal with that. But don't mess with it until it fails. You'll know when it fails because gear lube will fan out across the rear wheels and possibly also soak the rear brake drum shoes.
A few years ago I intentionally removed my "extended diff breather" on the rear axle to ensure that it's not the cause of my rear axle seal problems. Occasionally I still replace the (stock) rear breather just for the heck of it to ensure it's not clogged with dirt or causing rear axle problems. Other people have noticed that if someone has a dip in the routing of the extended diff breather line, gear lube can accumulate there and essentially plug the line, causing a build in pressure in the axle. The short while that I used an extended breather, I know mine wasn't clogged because I checked that. Still I have had repeated problems with the axle seals. There are so few deep water crossings now in Colorado that I removed the breather extension to be safe.
