I read through a majority of the reviews on the FJ before I bought mine. Every now and then there is a very low rating because of transmission or rear differential/transfer case problems. To those I ask, did you take your stock FJ in mud or water? If the answer is yes, that's why you had these problems. Unfortunately Toyota let the casual offroaders down. The problems you guys are having is because of the differential and transmissions breathers. These breathers let the hot gases/vapors out of your diff/tranny so they don't overheat. The problem is Toyota messed up with the placement. While these breathers are open to keep your parts from overheating, they fail to keep mud and water out.
Interior. Offroad capabilities.
Do not take your fj in mud or water deep enough to submerge your rear axle, transmission and transfer case without a 'scuba' modification. You will be posting a review about how you had to buy a new transmission. Google scuba mod. It's cheap and it will save you thousands of dollars.