Single knock under load *WEIRD!!

[Creager]

Everytime my truck gets that initial load a knocking sound is heard. It almost sounds like a (metal) slapping noise. I dont know man, its been occuring for over a year, it hasnt got any louder, it hasnt changed in tone or anything and its always garenteed to happen, i could set my watch by it.

I checked all the drive line. Wheel joints to the transmission, everything is tight and snug. I thought it might be the exhaust; i got under there an bent the exhaust shield back at all the choak points and i still got no change (THAT WAS NOT EASY!).

So im in the same place i was a year ago, what the hell is making that noise?

 

[IZwack]

I've read a few threads that matches what you've said - though it can still be many many things. Anyways, what I'm thinking is that you're rear drive shaft has gone dry. I forgot what it's called but its the joint that allows you to advance your driveshaft forwad (relative to the car's chasis) a little bit when you want to disconnect it from the rear differential. There are a few threads on this forum on how to grease this joint up. Try this first - its relatively cheap to do and shouldn't take too long.