Mystery Grind in Transmission, Engine, Where?

[ScoobyRoo]

I recently purchased a 1994 ETC with about 130k on it for 1800. The car looks wonderful but has a few flaws, one being when put into gear after its sat a bit (few hours) it will make a grinding noise up front for a brief period of time then quiet up. If its shut off then started up just after it wont make a peep, only after its sat a bit will it. Ive noticed that if I have my foot resting on the brake pedal I can feel it vibrating with the grind BUT it will grind without my foot on the pedal either way. Anyone else experience this? Ive been told in another thread that it may be the a/c clutch but I want to make sure. If the clutch pack was slipping would it make this noise as well? Tends to sound like grinding the gears on a manual but slightly softer.

[codewize]

How about sounding like rolling a coffee can full of marbles? Is that close to what it sounds like. Every time I've had an AC compressor go bad, that was the way I described it. Almost sounds like a water pump rattle when they have a bad bearing.

[ScoobyRoo]

Is there any way to figure out for sure if its that or not?

[codewize]

Remove the serpentine belt and spin all the accessories by hand. the bad one will feel rough or be difficult to turn. They should all spin freely. If they do, you have other problems.

[ScoobyRoo]

I've noticed that the car wont make the noise as long as you keep the rpms low when it starts up, but the moment you bring it anything above a rolling idle it makes the noise.

[codewize]

Does the car have to be moving for it to make the noise?

[ScoobyRoo]

Yes.

[codewize]

If the car has to be moving I'm guessing it's a wheel bearing. Pretty common failure. My transmission all but fell apart inside and made no noise at all until the very end when I was revving over 4500 RPM.

I'd be looking at the wheel bearings.

[ScoobyRoo]

I can roll around all day just letting the idle pull the car along like I said, it will only make the noise when I put my foot on the accelerator.

[99Classillac]

It could be your traction control engaging also. My 99 deville does it. I think my wheel speed sensors are bad. Dry or wet outside, if I'm stopped and try to accelerate even the slightest, the traction control engages and makes a horrible grinding sound. It goes away after a couple seconds.

[codewize]

Hmm interesting. Could it be CV joints? Does it click when you make a corner? It's definitely drive-line related but I don't think it's the trans. Could still be wheel bearing but that TC or ABS problem seems realistic also. If it's a wheel speed sensor you'll have a code.

[ScoobyRoo]

I hope its not a tranny problem, if it is I'm just selling the thing at a loss or not. I don't even want to get into a problem like that. Replacing the oil pan gasket and main seal is going to be enough as it is. When I get the time I'm going to pull more codes out of it, I got a set of ism's awhile ago and they describe being able to go MUCH further into the diagnostics than I originally did. I wish I could record the noise :P

[Zorb750]

Check for a loose hub. They can move slightly if worn and loose, while the engine torque is applied. I have had this sort of grind myself.