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Discussion Starter · #1 ·
I hope you can help me. First, let me start by saying that this is being written by a woman with absolutely no mechanical knowledge. We own a 2002 TB LTZ with approximately 180,000+ miles. We live 45 minutes outside of town so we put a lot of miles on a vehicle. This past winter we realized that our 4WD was not working when I got stuck during a snow storm. Lately when we drive the vehicle, there is what I can only describe as a grinding noise coming from under the hood. My husband says it sounds like a vibration, but it sounds more like metal-on-metal to me. It lasts about 2-3 seconds. It will make this noise about every 3 or 4 minutes, or it might just make the noise once or twice during our 45 minute commute - or it might not make it at all. There is no method to the madness other than it never makes this noise while in park or idling. Also, our 4WD switch light does not work. Sometimes when we start our TB all 4 lights come on and it makes a clicking noise. Obviously our Service 4WD light is on. Do you have any clue what could possibly be going on? Thank you.
 

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2003 gmc envoy_slt
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:tiphat Welcome :tiphat .The first thing to check is the fluid levels in the transfer case and both differentials.
 

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Discussion Starter · #3 ·
I checked with my husband and he said all the fluids are good as is the differential. Any other thoughts? We noticed coming in this morning that it seemed to make the noise when we would hit a bump in the road - however, it also made the noise when we didn't hit a bump. I'm thinking I just need to unload this vehicle and get something else. But I really like the Trailblazer.
 

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when you drive your truck and you hear the grinding noise did you looked at the speedometor and see when does it make the noise? Like somewhere around 35-40 mph?
 

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The 4wd not working, the intermittent 4wd switch light, and the 4wd service light on could be a separate issue, and just a loose connection or a bad switch.

Does it make the noise when you turn? if so which way, or both ways?
Does it make it while you're accelerating, braking, or coasting? Do you feel it or just hear it?

How did he check the fluid? Find any metal shavings?
Any play in either of the yokes or u-joints for the drive shafts?
 

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Discussion Starter · #6 ·
The weird thing about all this is that the vehicle drives perfectly fine - even when it is making the noise. It makes it at 30, 45, 55 and 70 mph. Not when turning. I guess we are going to have to take it to the shop. The noise is now starting to last much longer. But again, no difference in the drive of the vehicle. I'll let you know what I find out.
 

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The weird thing about all this is that the vehicle drives perfectly fine - even when it is making the noise. It makes it at 30, 45, 55 and 70 mph. Not when turning. I guess we are going to have to take it to the shop. The noise is now starting to last much longer. But again, no difference in the drive of the vehicle. I'll let you know what I find out.
Then it has nothing to do with the suspensions, ball joint, moog links and etc.

i have the same problem right now. only occurs at 35-40. I heard the noise at the bottom of the radio area. Im guessing its the transmission or the tc thats makes the noise.

Has the engine light pop up yet? If so, what is the code?
 

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Discussion Starter · #8 ·
No engine light. Just the Service 4WD light. Like I said - it only makes the noise when we're driving. It's hard to determine exactly where under the hood the noise is, but it's starting to get louder and longer. It's almost more of a clanging noise now. Definitely metal on metal. :bonk:
 

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Does it stop making the nosie when Truning right or Left? It could be a wheel bearing/Hub going out. usually, they will making a roaring noise and a vibration felt in the wheel.. If it is the wheel bearing have an independent shop due the work, cause the dealership will kill you in the price of a wheel bearing.

Another thing, it could be your front axles, they Can begin to leak fluid and start making noise before Failure.
 

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No engine light. Just the Service 4WD light. Like I said - it only makes the noise when we're driving. It's hard to determine exactly where under the hood the noise is, but it's starting to get louder and longer. It's almost more of a clanging noise now. Definitely metal on metal. :bonk:
yeah i know what you said and when it gets louder and louder your wheel hubs will break. i know that because thats what happened to mine 3 months ago. But we removed the 4wd parts so there must be something related to that...

But after replacing the hubs it still makes the noise, so it has to be something related to the 4wd parts...
 

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It only makes the noise when driving straight. Turning does not affect it. However, sometimes if we hit a bump in the road, the noise starts back up.
yes we know it makes noise when you drive straight. you said that many times and i told you many times that thats what happened to me even when i drive straight. my hubs end up getting destroyed

it could be the hubs, front axles or something with dealing with the 4wd parts.
 

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I guess you come by your name honestly. Sorry - I usually don't post on forums and now I know why I don't. I won't bother you any more.
normally when i talk, i talk in a joking matter. but since were communicating on internet it hard to express those emotions because some people might think im serious.

if i offend you i apologize. Im just trying to help you out.

btw my name came from dave chappelle
 

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2002 gmc envoy_slt
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I had the same problem when I put the truck into 4WD. I went to a meet at 7 President's Park last year and everyone thought it was the Transfer Case. I drained the TC, put new fluid in and still the noise. I gave up and took it to the dealer.

They thought it was the fork and bearings in the TC. They replaced all those parts and the noise was still there. Then they determined it was a transmission problem where the TC meets the Transmission. $1900 later :sadcry: it was fixed and no noise. I had a problem with the AWD where the tire would start skipping in parking lots. In AWD it shouldn't do that and it didn't for the first few years of driving the truck. Now after the transmission repair near the TC, everything is fixed. I still get my 4WD selector switch flashing lights every now and then, but I turn the truck off then on and it's fine.

I have a 139K miles on it. Original owner.

Let me know if this helps and what you decide to do. I'm curious to hear if it's the same problem. Let's hope it's not $$$$.

Can you please fill out your profile, so we have some info on the vehicle?
 

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OK - we all need to enter the 12 step program !!

My name is Rick and I am a GM masoquist - it has been 3 months since my last repair !! But now I need head and a front Diff !!

Somedays I think I bought a FORD by mistake....:bonk::bonk:
 

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:(:iagree: There's no sad face, I agree so...

OK, if no else will say it, I will, I sometimes, just sometimes, look for something to go wrong, so I can try to fix it...but just sometimes....:weird:
 

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check the front differential

i got the same noise about four months ago and i ignore it. now that became worst i saw some oil on my garage and i decide to check were the oil was coming from, i find out that the front differential was broken and some pieces of metal get in the differential gears.
now i have to replace the front diff.:worried:
 
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