I have never changed the tranny fluid and it has 167000 miles... I think its due for a change, however I heard it shouldnt be done.. Can I change the fluid or just leave it in there?
Transmission Fluid Change on 1996 Nissan Maxima
I would find it difficult to believe the transmission oil was never replaced. I would not use a flushing machine to "flush" the transmission but I would drive the car get the fluid hot. Drain the fluid, remove the transmission pan at the bottom of the transmission and refill the transmission with fresh fluid. A flushing machine may dislodge debris in the transmission which could be harmful, drain and remove the trans pan is not invasive but will remove the maximum amount of fluid and allow you to see in the trans for debris or damage.