Trooper 2001 transfer case fluid

The transfer case fluid from my 2001 trooper S 4x4 is seeping out so I've asked my mechanic to check it. He removed the plug and the fluid is kind of redish so he thought it was transmission fluid, but he asked the people at Isuzu dealer and they told him to use some kind of oil which is not the transmission fluid. So I looked at the owner's manual that came with the car and it recommended to use the 5W-30 oil. Does anyone know exactly what type of fluid does the transfer case use?

Thanks.

The standard t-case uses engine oil (5W30), the TOD case uses ATF.