Knocking sound coming from interior?
 

I've got a strange, very audible, knocking sound that appears to be coming from the dashboard/floorboard area. It usually starts after it has idled for a few minutes and increases with revving. I'm not sure if it's actually coming from inside the truck but it is very audible from inside the truck.

5.2l V-8 with 268,000 miles. I've only had it for the last 2-3k miles and have no idea what's been done previously. Any ideas?

This could be a number of things...

Firstly I would say its the gerbils telling you they're hungry. Just had to get that out LOL

But seriously, try getting under the truck and see if you can isolate the sound area where it's coming from, whether it be the transmission, exhaust, or wheel area.

To me it sounds like a possible spark knock too. I'd change the plugs with cheap Champion Copper, let me repeat that, Champion Copper! It is what our trucks like and is the only thing we suggest using, it's OEM. Also try a higher octane gas in it as you may just have some bad fas making its way out.

Get under it while its idling in Neutral with the parking brake on and see if you can't find out a better idea of where its comic from, rather than jut under the floorboard/dashboard.

This has become the least of my worries. My transmission is slipping into and out of gear. I think the miles are finally showing on this D.

If that's the case, I'd get a transmission fluid replacement along with a band adjustment and PRAY you don't see metal bits in the pan.

No such luck. She's in the shop now getting the tranny rebuilt. It was bound to happen sooner or later. I'm just glad it happened when I had a little extra money.