While there can be other causes, please also check steering knuckles. In case of viper seal or outer axle seal failure, grease can leak out of steering knuckles.
This is a common problem with solid axle Toyota. If that is the case with you vehicle then in the first instance try to tighten the viper seal (also called 'Namda' seal in mechanic language). If this doesn't solve your problem then a solid axle rebuild is in order. This is a time consuming process.
But again there could be other reasons of fluid leaks.