Brainstorm with me: Hissing sound from rear

OK, let me tell you the scenario before we start. I decided Wed. to head out to an area near Deer Valley Airport (zonies will know where I'm talking about) and play around on some hills that are commonly used by ATV's. The area is mainly silt, and there were still some puddles/ruts from the recent rain. I pulled up to this one hole, put it in 4lo, 2nd gear, and plowed into it. Right off the bat I knew it could turn out to be a mistake. My measly 31's sank right in (though it didn't look that bad at all) and my diffs were dragging between the ruts (probably carved out by 35+ tires). I managed to grab some sidewall and pulled on out but when I hopped out to look at what I had just done I noticed a hissing sound coming from the rear. I though "Oh crap, a tire," so I turned the Jeep off, pulled up the rear seat, got my tire changing stuff and proceesed to the back of the Jeep. When I got there, no hissing. Now I knew it was not a tire. I think I have located it coming from the tubes around the gas tank, but I can't be sure. I also noticed the Jeep is a little more sluggish and my Flowmaster 44 is drowned out bya new sound you'd usually hear coming from a dune buggy. It's not deep and throaty but rather light and rapid. I don't know much about mechanics, so bear with me. Could it have something to do with the rear axle; air pressure and what not? I'm not too concerned about it, as I know it's fixable, it's just bugging me not knowing what it is. I hear the sound when I press on the accelerator.

And here are some pix for your enjoyment.

Did you get crap in your exhaust pipe?

Only other thing I can think of is you pulled apart some joints in the exhaust system and now you are leaking around a gasket.

Only other thing pressurized back there is the gas tank, but I doubt the small amount of pressure that could leak from there would be audible.

most likley you are hearing your fuel pump working, Sounds just like a leaky tire

justin_502 said:

most likley you are hearing your fuel pump working, Sounds just like a leaky tire

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Not a leaky tire. Been two days and the tire pressure hasn't changed in either one of the rears. I don't think it's a fuel pump because I had never heard it before I entered the hole. Of course, I have been having starting problems lately. Could it be that all the jaring around caused some seals/gaskets to come loose? Maybe my fuel pump taking one more step towards pooping out on me?

Sparky, no crap in the exhaust.

Bad vapor recovery system/gas cap.

I noticed I'm leaking from the rear diff a little, or at least it's more noticable now. Also, my yolk/rear driveshaft (not sure what to call it) seems to have been pulled out some? I don't know if those things have anything to do with the problem, and I might be borrowing trouble with them, but I figured it couldn't hurt to mention them. Sorry the pics are grainy, it's getting dark.

old_man said:

Bad vapor recovery system/gas cap.

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What is a vapor recovery system? Is it fixable/replacable?