My transmission went out at 75,000 miles.
My fuel pump has gone out 8 times in the last 30,000 miles.
The interior panels and dashboard have cracked or lost adhesiveness.
This truck rides very smooth, but it does not handle as well as expected. I bought the Chevy because of the supposed good name. I was disappointed with the lack of longevity on the mechanical and electrical systems.
You could've had dirt in the gas tank that was never taken out, or you might have had dirt in the fuel filter and never changed that when you changed the fuel pump. Dirt in the fuel filter will cause the fuel pump to work harder than what it should, and eventually over-work the motor and burn it out.
My 1996 Silverado has the 305, and it doesn't have any problems with the tranny, and just turned over 120,000 miles on it. I've pulled a car trailer with a vehicle on it no problem. It might have been a bad tranny that was put in when it was new.