Noise while idling in Drive or Reverse - Silent in Neutral

[Edis06]

OK, I keep my HMMWV in a small garage which amplifies all sounds that emit from below the belt. When I start the truck, it sounds great, however once warm (or even after idling for 5 min or so) and you place it in REVERSE or DRIVE, it has a friction sound to it. It almost sounds like a constant friction/vibration sound but you can't feel any vibration. I notice this in the garage or if I'm outside the vehicle with the car in gear only. Also, if I pull up to a toll gate, etc., where the reflective sound is high. If I give it gas and start to move, it goes away.

It may have done this for a while, but it's become habit to notice one problem at a time and now that my cooling system is air tight, this is bothering me. Shifting is on point, with nice tight shifts and no drag going into or out of gear. I haven't changed the trans fluid yet but it appears very fresh. I did notice that when I check it while running, it's over the max mark, or at least it appears to be.

My gut tells me that I either have an aging bearing (trans thrust bearing, shaft bearing) or my torque converter is getting old. When I open the hood, it sounds much louder like it's coming from the engine, but I know that must be just transmitted sound via the block.

Here's a vid clip of the noise:

Any ideas?

 

[TOBASH]

Not sure what you're worried about. Mine makes the same sounds in and out of gear.

In gear the engine gets loaded with forces against the torque converter and clutch plates . It slows down and needs more fuel to rotate while also loading the torque converter and transmission components. Perhaps that explains what you're hearing?

 

[Milcommoguy]

Here's what I hear with a grain of salt........ Easily hear the Cadillac valve a "hissing" Clunk in to gear just like mine, "Run Run Run" noise like it's ready to go for a run in the woods. Do you have the modified flywheel cover? (has been cut to easy in / out starter) I do and with all the shaking / vibrations it would rattle at the cut (Kerff area) like truck was going to blow up. Opened up the gap between the two pieces. No more buzzing - clanking.

Best to get the stethoscope out and snoop around. Old truck could be old mounts engine or tranny. Something moving around under loading? That's my two guesses limit with limited data. Good luck and watch out with spinning parts.

Salty old dog with bad hearing, CAMO

 

[fpchief]

That is how my 200a alternator sounded before had new bearings put in it, however it made no diff in neutral or gear.

I hear it, there is something there. Camo gave you great advice. Stethoscope and start investigating.

 

[Edis06]

Thank you all for the great advice!

I am leaning toward the vibration sound as opposed to bearing and here's why: When I started it this morning, the sound was there in Neutral but not while in gear. Once warmed up, it was gone in Neutral and present in gear. Also the fact that it disappears as soon as I give it gas suggests that it is frequency related.

Out of all the tools in my garage, I don't have a stethescope. I'll be picking up one today!

 

[fpchief]

Long extensions, or multiple extensions work just fine too.