Transmission won’t shift past 4th gear

[Olerustybrown]

I’ll Just bought my first Lexus 03’ GX470, 186k miles. I noticed when I’m driving in normal conditions that I can’t downshift or even move the shifter to neutral. So I thought huh that’s weird, maybe it’s a Lexus thing. Next day I thought I’d try out the four wheel drive. With the transmission in neutral, I shifted the transfer case into low, then tried to shift the transmission into low, it would not go past 4th gear. Yes, I’ve read the owners manual. Has anyone else experienced this? 

Edited March 1, 2019 by Olerustybrown
Incorrect mileage