I have an 03 Silverado 1500 with the 4.8L engine. For the past two years I have been towing my friends speedboat up north to the lake on memorial day weekend. The first year I towed the boat I had the stock exhaust and obviously I could feel the trailer behind me, but it wasn't that bad.

But this year when I towed the boat, I had my Flowmaster Cat back American Thunder system installed. It seemed like the truck lost some torque on accelleration. Without the trailer it feels fine. I read somewhere on this forum that cat back exhaust systems rob torque. Any truth to this, or is it all in my head?

 

i have not heard anything like that before doesnt mean it cant happen. it couldhave aback pressure problem. i ran a cat back system and could definetly feel the difference with my truck. i switched to true dual and it seemed to run alot smoother even with a trailer.

 

Depends on year/make/model of the truck. I'ver heard alot of torque loss issues associated with the 4.8 and the 5.3 (99 to 05 mostly) and the use of aftermarket exhaust. These trucks need all the backpressure they came with to make the torque. Try this out to make certain; Buy exhaust reducers from a parts store that would reduce the tailpipe diameter by an inch or so, (leave the stickers on and wedge them as best you can so you don't need clamps this way you can return them). If you have tips, find reducers that will fit inside the tips. You are just trying to plug the exhaust a little. Drive ther truck with a load on it. If it pulls better it is simply a backpressure issue due to the performance exhaust. Otherwise you might have a bigger problem. Fix for the performance exhaust would be:

1. A programmer or tune
2. A reducer somewhere on the exhaust
3. Smaller tips that will act as reducers
4. The use of higher octane gas
5. They make pretty nice exhaust tips with reducers or butterfly valves in them
6. Smaller tailpipe sections (Ex: 2" instead of 2.5" tailpipes)

 

is their an exhaust i can put on a 2003 5.3ltr truck with no power loss and still have a good sound....

 

Keep in mind that this torque loss can probably be tuned or programmed out if the person knows what they are doing. For those who want to keep it simple:

You might want to try doing just a muffler to replace the factory muffler. Throw on a Flowmaster on or something but leave the tailspipe go. It will be pretty quiet but your torque will be there. Want more noise you can either use a glasspack or you can also try buying just the muffler (1 2.5" or 3" inlet/Dual 2" outlets) and have an exaust shop throw on the dual tailpipes. Only use 2" or so as most exhaust systems are 2.5" or bigger and there has been some torque loss due to this especially when towing.

I used to have a 91' GMC 4X4 with a 5.0, no cat, vortec heads, cam, complete MSD ingnition system, lower t-stat, programmed, tbi from 454ss, throttle body spacer and K&N cai. I used a flowmaster with dual 2" pipes and had enough umph to haul 1000lbs loads of scrap every weekend with no problems, but this was an old tbi engine, not a GenIII. Im sure having no cats on a newer truck would have killed the torque a bit more.

 

I've got an 02 2500HD with the 6.0 and I put a mufler with a duel in and a single out and it still had great power with awesome sound. so if you don't think you have to have the duel mufler system you might try this because they still have great sound and you don't lose any torque