Hello asking for my dad,

He bought a 99 K1500 with the 5.7. He bought it from marketplace and after driving it halfway back home the tranny went out. He got it replaced and the transmission shop made a big deal on how they were going to help him out and give him a great built tranny for the same price. Then he drove the rest of the way home.(1400 miles). That was a couple of years ago now, The problem is that there is no top end power. If you go to pass someone and floor it, it does downshift but the second it hits 4K rpm it hits a brick wall in terms of power. It starts running real bad and again just doesn’t have any more power. It’s weird because if you just accelerate normally it has plenty of power and runs great. What is the most likely problem? My dad seems to think it’s the transmission.

 

When is the last time it had a full tune - plugs, wires, cap, rotor, all filters etc?

 

[QUOTE=Rednucleus;508347]When is the last time it had a full tune - plugs, wires, cap, rotor, all filters etc?[/QUOTE
plugs and wires were done when he bought it. As well as air filter and oil filter. The times that it has been in the shop the mechanics struggled to get it into the correct timing so I’m unsure of that. I keep on telling him to change the fuel filter… but he hasn’t done that yet.

 

Just an update… he got it fixed finally! It was that the PO was a “mechanic” and was so good that he replaced the fuel filter the wrong direction. And the passenger cat was clogged. Put new rear shocks in as well and now she runs good as new! Thanks for your answers!!

 

As I was reading your post I was thinking it sounded like a fuel issue. But about the fuel filter, did you replace it or just flip it? Reason I'm asking is it might have put a bandaid on the real problem and that's the fuel pump. I would just for grins check the fuel pressure and see if there's anything wrong or different between the two readings.