NOW what? GMC Terrain SLT LOUD noises ! And suggestions

General Discussion
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Have only had my 2021 GMC Terrain SLT 2 months, almost to the day, and yet another unexplainable thing happens.

2 weeks ago I was in a Target parking lot. Came out of my parking spot and drove about 5 car lengths, having to stop for people coming out of Target. As soon as I do there’s a VERY loud CRACK sound from the front right passenger side. Felt it in the steering wheel and the car itself. Like if you’re sitting in the car and someone slaps it with their hand really hard. That kind of feeling. First thought was someone threw a big rock at the car, which didn’t make sense because I was in a parking lot, but that’s where my mind immediately went. Even though there were cars behind me and one to my right waiting to pull into my lane, I immediately got out of the car and went around to the passenger side to see what happened. When I got there, the guy in the truck to my right had his window open, and I asked if he heard that crack sound. He said he did. Didn’t see any damage, nothing on the ground underneath, so I went home and called the dealer to get it in. Couldn’t get me in for 2 weeks. That was today. Took it in this morning. But before I took it in…

Last night, the EXACT SAME THING happened, only THIS time it was MUCH worse. Again, I was driving on the road (about 30 mph) and had to stop for a red light. I come up to it and stop. Didn’t ever slam on the brakes. I was coasting up to the red light, so came to a gentle stop. As soon as I come to a COMPLETE STOP, a split second later the same CRACK sound happened, but this time it was 10x as loud. I mean alarmingly, scary loud. Same front passenger side. The whole car shook. My body moved. The feeling was as if there was a really heavy something in the back seat that slammed into the front seat as if I was going 30 mph and slammed on the brakes. Only my back seat is empty. Nothing in there at all. Or in the trunk. Nothing there either. I honestly thought something broke off the car underneath. Because I was in a very busy intersection I couldn’t get out of the car to check, but I was going to my son’s house which was about a mile away, so I just went there. Again, didn’t see anything on the outside, though it was dark out now. Was really afraid to drive it the 22 miles home, considering the immensity of the sound and feel, but I drove slower than normal and hoped nothing would happen before I got there.

So that next day, today, took it to the dealer. I knew he wouldn’t be able to duplicate either event and I told him so. Typical car event - that when something happens with your car, you take it to the mechanic and it doesn’t do the same thing and he can’t duplicate it. Anyway, he said they drove it twice and put it on the lift to look underneath and didn’t find anything and couldn’t duplicate it. Then he said he was “suspicious” and skeptical (like he didn’t believe me) because “it’s not like it happened a lot, it only happened 2 weeks apart, which doesn’t make any sense.” His words.

The car had 14.5k miles when I bought it 2 months ago. I put almost 400 miles on it in those 2 months. Other than the headlights issue in the beginning, car’s been fine. Now THIS happens. And this service guy doesn’t really believe my description of events, what it sounded and felt like. Like those things are impossible to happen.

Just if there’s any relation, this happened about a month and a half after having the underside rustproofed. Don’t know if that has any bearing or not. One of my thoughts about it is that maybe there’s a place under there where 2 spots meet, they rustproofed over that spot and it was that “joint” that broke apart and made the crack sound. Although I would think if something like that was even possible, it would happen while driving, not after having come to a complete stop. And not loud enough or forceful enough to shake the car and make my body move.

So here’s what I’m thinking and need suggestions for, because it’s the only thing I can think of - I want to buy the best recorder possible - don’t care what kind or price, because it has to be the best to do what I need it to do, and that’s to hopefully record this sound if it ever happens again. Need type to buy. Since I don’t have anyone who can drive with me every single time I drive my car to be a witness, the only thing I can think of is to record it. Turn the recorder on every time I drive the car and hopefully it will get at least the sound of the crack. Unfortunately only an actual person sitting in the car would be able to witness and feel the movement that goes along with it.

If anyone has ANY idea what could cause this event to happen - twice, one much worse than the other - please let me know. I’m extremely concerned about it, but I have to drive it unless somehow it can be identified and fixed. Of course, no one’s ever heard of this happening, and it’s not just an anomaly, it’s an impossibility.

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Welcome back Ms. Remodeler, sorry you are having this issue…

And this happened while Not moving after coming to a complete stop, correct??

Gonna have to think about this one… :thinking:

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As you come to a stop, and bang. Brakes are being applied and released slightly. Perhaps a brake caliper or mount bracket is loose/binding? I don’t see how a suspension strut or control arm could have much wear in 3yrs/15k miles?
Terrain has reg v6? Not a turbo 4 setup? Not hybrid. Does have elec power steering. Awd I assume? Cv axle binding?

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On the legacy trucks, this sounds just like the driveshaft yoke sticking- where you get a big bump after coming to a stop and the yoke finally yields to the stress on it. Which makes me think- is it possible something similar is happening to your right axle? Something is broken or allowing it to come out of the retainer and then when the car comes to rest, it snaps back into place…

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You’ll probably have to take it back to your shop when you figure out how to get it to repeat the sound. My guess is a broken suspension spring. The break can sometimes be very hard to spot. Maybe your shop has a way to make cracks in metal more visible.

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Thank you. And yes. Complete stop. Second later the crack. Both times.

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This is my car: 2021 GMC TERRAIN SLT AWD ENGINE: 1.5L TURBO DOHC 4 CYL 9 SPEED AUTOMATIC.

Don’t understand the comment “Brakes are being applied and released slightly.” I held the brake, didn’t release it at all. Unless you’re saying it does that internally. And not “as you come to a stop” - I was at a complete stop when it happened.

Dealer said they didn’t find anything and they couldn’t duplicate it. I told him he wouldn’t be able to. It’s not like it happens all the time. It happened twice in 2 weeks.

Can’t answer any of your other questions about elec power steering or CV axle binding, since I know nothing about cars…

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Can’t imagine there’s anything I can do to, as you say, “figure out how to get it to repeat the sound.” It happens randomly. Nothing I do makes it happen, other than just coming to a complete stop.

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Unless you have an extended warranty they probably won’t even really look for a problem . If your paper work says ( Sold as is ) they have no responsibility to fix it anyway.

Maybe you should have taken my advice and bought new within your budget.

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I do have an extended warranty. Nothing says Sold As-Is. They also have their own bumper to bumper 6mo/6000mi warrranty.

I also understand they have no incentive to find anything wrong that they can’t bill me for no matter if there’s a warranty of any kind or not.

And again, there wasn’t anything new in my $20-22k budget that had what I was looking for, as discussed in that thread.

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Don’t know what a legacy truck is. Is that what I have? Should I take it back and ask them to look specifically at the driveshaft yolk and right axle? Obviously something is happening intermittently to make this scary sound.

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Does it happen every time you come to a complete stop? If so, I’d be surprised your shop techs can’t figure it out.

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Just another post where the poster did not READ the OP’s post that it has only happened twice in 2 weeks and clearly stated at least once that she can not duplicate the noise…

2 Likes
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This is what the OP says above:

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There I fixed it for you.

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You missed the first part of that quote - that part where I say “It happens randomly.” As I also said, it happened twice in 2 weeks. So no, it doesn’t happen every time.

Sorry, guys, I didn’t see the posts where you told him the same thing before I posted my reply. But thanks.

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Do you think that might have been the action of the engine starting? The sound of the starter motor when in a confined space can seem rather loud and there can be a bump feel when the engine starts.

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It’s OK, that is just what he does, picks and chooses what he wants to read, and simply takes everything out of context…

I am starting to think Twin Turbo is onto something, about the only thing I can think of is, your rear driveshaft (propeller shaft) is somehow binding up from the undercoating, it looks like (can’t find any good pictures) it has splined female couplings w/u-joints at each end with a center support bearing and slip yoke and one could be binding after kind of a hard stop once the engine/transmission shift back into place so to speak…

It is about 63" long and runs from the front to the back of the vehicle connecting the transmission to the rear end (loose terms)…

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It didn’t happen when I started the car. I drove for about 5 or 6 car lengths and when I came to a complete stop, that’s when it happened. Both times.

And there isn’t anything like you state when I start the car. No nosies, nothing, just the car starting. So I can’t imagine it’s the engine.

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Thank you for that. I still think it has something to do with the rustproof coating, and it may be that. Maybe it won’t happen again since that joint? now “cracked”. Will have to wait and see.

Just one other thing - it wasn’t a hard stop, as you say. To me, a hard stop is like slamming on the brakes. That wasn’t the case. I was in a Target parking lot doing, what?, maybe 5 mph, stopping for people, then going maybe another 2-5 mph before coming to a dead stop. But that doesn’t negate what you say could have happened.

But now the thing is, the rustproofing place says I come back every year to get “topped off” as it were - that they respray places that it fell off or wore off or whatever rustproofing does in a year’s time. And if they do that, will the same thing happen? If they cover that same joint (I don’t know what else to call it) will it crack again? If so, I guess I’ll know that was the problem. But I’ll have to wait a year to find out. That is if it doesn’t happen anymore.