One problem related to axle shaft seal has been reported for the 1999 Toyota Tacoma. The most recently reported issues are listed below.
The rear axle seals are leaking. The rear axle fluid is dripping on the brake drum. This is throwing the rear axle fluid onto the shoe, causing the brakes to lock up. The driver almost had an accident as a result. This incident occurred snowy weather while making a turn. The rear end would lock up at slow speeds and wouldn't unlock until it was given gas to start up again. When the brakes locked, the vehicle slid into the curb.