I have been reading the post for a long time but I seldom ask question. I have long realized that you are an expert in automation transmission. I know you recommend to change the so called life time fluid. And I remember you mention changing the fluid on a long negelected trans. will cause problem.
I have a 97-740il with 40K, and a 95-540ia with 70K. Both have original life time fluid. When should I change the 740's ,and is it too late now to change the 540's.
When is the optimal time to change the fluid.