If there is any chance that the T-case or transmission you are about to buy has had water in it for a few days, weeks, or months, it could be an expensive and rusty paperweight. If an older T-case is not bolted to a transmission, you should be able to look inside. If a transmission’s all sealed up, you may be able to pull the top cover/shift tower. Just make sure to get the shift forks back on the shift collars. Also, some transmissions or T-cases may have a PTO cover you can pull if so equipped. If there is rust or water in there, walk away unless you are just buying for parts like a shifter or case/housing.