I have 37s on mine. Ive talked to a lot of people about breaking shafts and it came down to this, the guys that looked like they would break shafts end up breaking hubs and shafts even when upgraded,, the other guys that are more calm have told me they have wheeled for years on stock parts and large tires. I took mine to clayton and bought two spare birfs from Fjaggie and never used them. Just broke my aluminum blocks. I see guys breaking hubs more than anything else on the toyotas and thats why the factory hubs are going up in price all over if you can even find them, the best way I found is just buy IFS hubs from ebay or guys that are throwing them out for cheap ($20) and then buy the $60 chromoly hub gear from marlin crawler (I think) and that converts the IFS hub to a chromoly solid axle hub. Thats how my spares are sitting right now but I dont want to put them in because I want to keep the hub the weakest link..