This may be a dumb question, if it is I apologize.

I've been trying to research the hell out of the Transmission issues our trucks have, and it seems like people are having a hard time getting it to shift crisply at redline.

My question is - Isn't running an engine at redline bad for it? Growing up I was always taught not to "tach it out" out of fear of putting undue stress on the engine.

I realize the 6.1 is meant to go fast, but do any of you guys worry about premature breakage?

For a performance engine such as ours, it's designed with this in mind. "Redlining" it is perfectly safe when the engine is up to proper temp, etc. The TCM programming on the current trucks is designed to shift when you see the needle slightly into redline. It will auto-upshift, which was something I made a thread about previously.

You are correct in the past before computers were put in the mix over revving would toast the internals. Now not so much.
You should be fine with the rev limiter this will stop it from actually over reving and sending a rod out the side of the block.

once the programming end of our motors is figured out we have to be very careful of how high we set the rev limit though.