I had the same problem. I opened the back of the seat and added more padding to it. It has helped a lot plus remember to sit in the middle of the seat. I was leaning to the right with my elbow on the arm rest and this was half my problems. Damm I miss those LS 400 seats now!!
If you change the transmission oil when you change your motor oil when should you change the transmission filter and is there a filter?
Thanks new member 2nd ls400 current model 98 LS400 97,000 miles