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Q: Odd chattering noise, when I start the truck up cold. Goes away when I drive it. on 1991 GMC Sonoma

To give a terse history, I bought mine for 400 bucks, from a 17 year old farm boy who drove this thing into the dirt. For some reason or another, earlier this year, I took care of one problem, where it sounded like a rod knocking. Turned out that when the kid worked on the transmission, he didn't torque the bolts at all. So I took care of that best I could and got the bell housing bolts in tight and it no longer makes that noise.

To add, my starter bolt for some reason is going loose, and it so cramped to get to it, cleaning it to have loctite work to keep it in has been impossible for me. So every few days to a couple weeks, I tighten it up. Funny thing is, my 14mm socket keeps getting stuck on it. Is it a 9/16th bolt? Is that why the metric socket is getting stuck?

Since then, I've been able to fix most everything, but since I am only self-taught, I can't for the life of me figure this new problem out.

Just awhile ago, when you start the truck up cold, it makes this rotating chatter noise. While in park, or driving at slow speeds, it chatters away. While driving, it goes away, although sometimes you hear a low squeal and grinding noise for a second, then it goes away.

Last weekend I noticed my U joint was a touch loose. Not sure what the tolerance is, but I've let that go since then (I'm broke now), but I checked it as I was replacing my CV axle and bushings on my brakes.

I checked everywhere with my stethoscope, and the engine is running like a watch (well I need to fix the timing a bit), the transmission shifts fine, but one thing I did notice was this.

Turn the wheel to the left, in idle, in park, no problem. Turn the wheel to the right, in idle, in park, and the chatter goes faster.

From my experience, I am only coming up with 3 things. Bad U joint, bad bearing (which bearing I am not sure) or the power steering (but the reservoir is full and doesn't leak). I just know that while in drive, sometimes turning right is a chore. You have to sometimes man handle the steering wheel at low speeds to turn right. Turning left is fine.

If you can help me through this, you will be my personal hero(s).
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The answer to your questions:
- Yes it is a 9/16 socket sized bolt
-U joint has "0" tolerance ,if t has any play they are needs to be replaced.
-The chatter most likely comes from the power steering pump

Check fluid in power steering and if it is dirty (dark in color) and smells bad you may try to flush the system. If this wont help you may have to replace the P/S pump.
First off thank you.
As for the bolt. Worked great, thanks.
As for the U joints, ya I can feel it pop up and down, although visually did doesn't appear to physically move.
I came across an article about a main bearing going out that sounds a lot like the sound I am hearing. Back in June, I replaced the Harmonic Balancer (clutch fan). I remember seeing a tiny slip of paper fall out of the box for the new one, that said to turn the fan a few times to get the oil distributed well. Since I just went by my buddy's advice over the phone, I didn't think anything of it. Nothing happened over the next couple months, so I never gave it a thought.

The pulley on the bottom seems to be the source of the chattering, so if a main bearing (or crankshaft that is broke) is the problem, I heard it can take out the water pump, but can it take out the power steering pump too?

As aforementioned, what it seems like, still might not be right either. Near the torque converter, the noise is loud too.

Sorry if I just confused you or anyone else. I'm trying to give as much info as possible. Thanks again.
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