I purchased a 2013 lx with 86,000 miles last year. it was dealer maintained. no record of differentials, transfer case, tranny fluid being changed.
1. First thing, I spoke to a few lexus dealerships in my area. Not a single one would do a transmission fluid exchange and/or drain/fill. the usual song and dance it was sealed. I did speak with a service advisor at a lexus dealership and he stated on his personal lx he exchanged it at 100,000 miles. I went to an independent mechanic and he did a fluid exchanged. He stated he used toyota ws. Once it was completed and I received the receipt and it stated generic synthetic fluid. I paid ($200) him but not happy. I went to a toyota dealership (about $200) a month later and had fluid exchanged again with world standard. I have put a link below on why you want to use ws according to professer kelly.
2. I found a mechanic off this board. I purchased the toyota transfer case fluid. I purchased differential fluids (mobil one) and crush washers. I was charged $59 for labor. I had front, rear differentials changed. He stated it look very clean. No lights have ever come on.
My experiences....