I’ve experienced that in my ‘01 LX470. Ended up being a bad u-joint. Wondering if the incline could be putting more torque on the driveline to make it more pronounced.
I use https://partsouq.com/
This is the specific link for my 2001 LX470
You can go here and input your VIN and it will take you to the correct model/frame etc. Great resource for finding part numbers.