Automatic Transmission issues
 

I have a 2004 350z with and automatic Transmission and 110,000 miles. Its had issues after I got it and wasn't aware when I bought it. I got the transmission fluid changed while it was still reddish brown but hasn't fixed the issues. It grinds after 10 mins of driving or once the transmission gets hot, and it also sometimes has a 1-2 second delayed engagement between gears from time to time. Sometimes it shifts instantly though and makes a bang noise into gear 3 and feels like the car is catching. Any help or advice would be nice.

If fresh fluid didn't do it and the fluid level is correct, its probably toast.

You could try an ECU flash just as a last measure, but best bet would be to take it into a mechanic to get it examined.

But with new fluid, you're looking at a hefty repair/replacement bill in the near future. Maybe see if the issue still exists with you manually shifting the Z?