when should the tranny be serviced on a 99 z-28 and what kind of fluid should be put in for best performance?

 

I have mine serviced every 15K, which is what I believe the recommended service is for most transmissions.

The place I bring mine to uses Pennzoil fluid I believe.

If you just bought the car, see if the fluid is red. If it's red it was probably just serviced, but if it's dark and tarnished, it would be good to change it and the trans. filter right away.