Can an exhaust leak only make noise @ certain RPM's? I have a hollow sounding noise which sounds like it coming from the exhaust but it only happens between 1250-1750 RPM. Could this be a hole in the exhaust? It also seems to be worse the more I load the engine. If i'm sitting in neutral it still does it but not as bad as if I put it in 4th gear and try to take off from 15MPH. Any insight would be great...

 

An exhaust leak is a leak. Althought the leak can sound worse as RPM's increase.

If it is a leak, you should be able to start your vehicle and set the emergency brake and crawl underneath and run your hand around the exhaust system (notice AROUND, not touch) front to back. If you have a leak, you should be able to feel it, or perhaps see an actual crack/break in the system.

I am thinking that there might be something else going on, but we will need more information on your vehicle to help pinpoint what may be going on.

 

i got my exhaust done yesterday. SI/DO MellowTone muffler w/4 inch chrome tips straight out the back. On the way home from work (muffler shop was across the street from work, so didn't really drive it much until after work) i noticed that starting at about 3500+ at full throttle the exhaust would "whistle". I took it back this morning and he put it on the lift and while it was running he did as described above, feeling for leaks. He found two, and both were on top of the pipe/welds where he couldn't reach to weld the leak. He put some "mud", as he called it, on there and let the truck run for about 15 minutes to make sure the exhaust was good and hot. No more leak.

So the answer to your question is yes, an exhaust leak can only make noise at certain rpms and/or engine load levels. It's weird that yours only does it from 1250 to 1750 though. Typically an exhaust leak will get worse as the RPM's raise. More air flow = more pronounced leak.