94 big block under dash ticking

[PlanetExpressShip]

I've got a Chevy 3500 with the TBI big block. I regularly tow my 5th wheel with it and I've noticed a ticking sound coming from under the dash. Kind of around my feet. Maybe more toward the center. It's a sharp rapid ticking, and rather quiet. It's only been present when we are towing and going up a hill in the middle of the rpm range. If I punch the gas and drop a gear, ticking goes away. If I let off the gas, ticking goes away. I'm talking about going the speed of your average semi truck. Maybe a bit slower. I'm not winning any races here.
I haven't noticed any other symptoms. No electrical stuff happens with the ticking. No power loss, no misfiring. Nothing weird at all. Just this obnoxious and scary sounding ticking. And at 6.5mpg, I try not to push the truck too hard. Any ideas? The trailer is also my house, so if there's some preventative stuff I can do, any input would be great.

 

[someotherguy]

Either an exhaust leak (manifold gasket, joint to the Y-pipe, etc.) or it's pinging. Check for any indications of carbon/soot around all the exhaust.

Richard

 

[PlanetExpressShip]

Either an exhaust leak (manifold gasket, joint to the Y-pipe, etc.) or it's pinging. Check for any indications of carbon/soot around all the exhaust.

Richard

When it warms up a bit outside, I'll check for exhaust leaks. I know my pipes after the mufflers are full of quarter sized holes. Would the pinging go away if I used higher octane gas while towing?