I have a loose bearing, let me describe it:

• it sounds like marbles hitting each other (not crankshaft/engine whir)
• sounds like under front of truck (not wheel bearings, just replaced them)
• when I accelerate, it makes noise - the faster/harder accelerate, the more noise. when I cruise with foot off pedal, it doesn't. when I'm in neutral and moving, it doesn't.

So it looks like only when the transmission is under load that it makes noise. I'm not sure what it might be since the transmission was rebuilt last year and it's got enough ATF in there. But it might be related to that. Please help me diagnose, thanks.

 

Spark knock?

 

X2! This could be pre ignition, Hot spot in the combustion chamber.


Bad or spun bearings... If the bearing/s are worn you will hear the engine make noise until you build oil pressure(as soon as you start it). A spun bearing you will hear after it heats up usually slightly higher than idle(depending on what condition it's in). You can you give more info like when do you first here it. A sound clip(video, post it on you tube and link it here).

 

I will make a video and post it. Thanks for the spark knock idea. For the record the plugs look okay, I don't know about gap but they looked normal last I saw.

 

thanks it does sound more like knock after hearing again

 

try adjusting the distributor see if it makes a difference. hard to say if it would. what year is the truck? 90?

 

1989, had EFI stock but that was all changed awhile ago to carb and deletion of all emissions systems.

How would I adjust the distributor... just moving it one way or the other? I recently took it off and cleaned it for another issue and put it back where it was before. But I'm not sure if this sound was there before or not since I bought the truck a couple months ago.

 

i could tell approximate age from the key. that is the newer style key. never seen a 89 with it but knew it might be possible.

just have to rotate the distributor. i believe you need to rotated it whichever way makes the engine idle lower. if you had the distributor out you may have messed this adjustment up.

 

I'm wondering if it's preignition after reading http://www.misterfixit.com/deton.htm

Sometimes when I shut off the truck the cylinders still fire for a few seconds. But the thermostat never shows the engine as running hot - which I know could be defective possibly. I know there is enough coolant in there as well.

 

timing being too far advance can cause sounds like you are having and for the engine deiseling on when you shut the key off because the cylinder is getting too hot. stock temp gauge is junk along with the amp gauge. oil pressure one is ok along with gas gauge when everything is working.