99 gs400. we just bought it a few days ago. when backing up in reverse up something like a steep driveway, it feels like it's "slipping" or binding like it's a locking limited slip differential. is this normal? this condition does not happen on flat ground.

 

This does not sound normal. Did you buy that one modded car? if so, what are the exact rima nd tire specs on that car? I am thinking it is something more basic that what you are thinking and I don't think you can fix it completely. I have a feeling that your tires are hitting your fender but I wanted to confirm that with the wheel info. Depending on how fast you are moving, the feel and noise will be worse.

Well, if it is not this than maybe someone else will have an idea.

 

i don't have the wheel offset , but the rears are 20x10, and i think the fronts are 20x9.

the rears are 255/35/20 falken azenis, brand new.

i was trolling the archives and found someone else with the exact same problem on a gs300 but there was no post on how it was resolved:

https://www.clublexus.com/forums/performance/60163-99-gs3-34k-mi-jerks-moving-slowly-in-reverse.html