Engine/Transmission (1994 - 1998) what is knocking?

[JAmos]

My truck has developed a knock/vibration that is very intermittent. The knock/vibration feels like it is coming from under the floor, anyone inside can feel it. The truck will go for a couple days or couple weeks without the knock/vibration then do it again. When the engine is turned off and has been vibrating it sounds/feels like the pistons are coming out of the block. It will make the knock/vibration when moving or idling, in gear or clutch pressed to floor, which eliminates everything but the engine as the source right? No loss in performance or oil pressure at any time. No more smoke than usual. I was wondering if something in the injection system might be sticking but runs the same all the time. All fluids look good/are full. Drive shaft seems good. Don't know what to check next. Loud pipes save lives, but I don't want to sound/feel like a rattle trap waiting to fall apart. I can usually make the clutch slip if I hit 4th gear too hard, but if its the clutch wouldn't it make the noise all the time? I will try to find any more specifics, but weather doesn't seem to affect it, and I always drive it like I stole it(is there any other way?)

TIA Jordan

 

[JAmos]

I would really appreciate some input on this, would like to fix the problem before it becomes a big problem. The properly valved minds must know something.

Jordan

 

[JGheen]

When was the last time you adjusted your valve lash?? Have you checked the lift pump for any noise?? I could make a better asumption if I was there listening to it, but not sure since you said your performance and everything else seems to be operating fine.

 

[JAmos]

Think I adjusted the valves last summur/fall. It never vibrates/knocks when I have time to look at it, only when I am busy, so wish I had more clues to give.

Jordan

 

[JGheen]

Well, I would check them again unless you think you have not drive the truck over 30,000 miles between now and then. How many miles are on the engine?? One should adjust the valves every 25,000 until over 100,000 miles and every 40,000 after that..... at least that is what I was told. Anyone hear anything different?

 

[JAmos]

176k+ miles and maybe 7-10k since last adjustment

 

[JGheen]

Well, I would rule out the lash then. Any other symptoms besides the knock?? Still no performance or fuel mileage loss? Did you check the lift pump for any noise? All your pulleys are ok and noise free?