Unfortunately built transmissions cost money and for most companies they will NOT stand behind them if they break.

the 4L60e which is in 4th gen F bodies is a classic example of a transmission that should have never come in these cars. Its been well over 17 years since the introduction they companies that specialize in them are finally getting them to "live" behind big power cars.

Just having good parts in a transmission will not guarrentee it to survive, you need it take it to a place that specializes in that transmission. It does make a difference.