2000 Z71 Transmission noise

I have a 2000 5.3 v8 auto. Each time I put it in gear I hear an awful grinding noise.seems to last for a second or two and then the truck goes into gear. Shifts rough once in gear and then when I come to a stopl light the truck idles really rough. I usually have to put it back in neutral.

Scanner is giving me a generic code of P1870.

Any ideas? TCC?

Thanks.

That code is often thrown due to wear in the control valve body, usually in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.
The reason you're getting harsh shifts is because that code is telling the pcm to produce maximum line pressure, which results in harsh shifts.

The correction for this is usually replacing the valve body with the revised TCC regulator and isolator valves, found in all the transmissions made after January 15, 2000.