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[VIDEO] Loud thud, car shake while driving low rpm
hey guys, so I’m having this issue and I can’t get a grasp on what it could be. While driving, after the car is warmed up and after some driving, my car gives out a loud thudding from the rear and it’s so loud and violent that the entire car shakes. Only happens while rpm is low and the road has some imperfections. It feels as if something is slipping. The rpms shoot up while thudding and then drop back down. Initially I thought it was the diff so I found a used low mile one at a junkyard and swapped it out as well as swapping all the diff bushings to whiteline. I also changed the endlinks while I was at it. Overall the car is stiffer and the thudding isn’t as violent because of the new bushing but it’s still there. The only other thing I can think of is maybe the tires? |
rear axle shafts loose?
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I'd get under it and pry around on every single suspension or driveline component to find out what's worn. If it had a bolt or a bushing then it has the potential to fail, also inspect for broken welds. Re-torque everything, including the subframe bolts.
Are you sure you don't have a slipping clutch? |
Originally Posted by SoCal04G35
(Post 7136677)
rear axle shafts loose?
Originally Posted by cleric670@gmail
(Post 7136678)
I'd get under it and pry around on every single suspension or driveline component to find out what's worn. If it had a bolt or a bushing then it has the potential to fail, also inspect for broken welds. Re-torque everything, including the subframe bolts.
Are you sure you don't have a slipping clutch? I just don’t get what could cause such a violent reaction. Makes driving unbearable. My tires are starting to wear out. Could that have anything to do with it? |
Check your AT fluid level, it could be running low on fluid then you get a sudden burst of torque as line pressure builds up.
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Originally Posted by cleric670@gmail
(Post 7136689)
Check your AT fluid level, it could be running low on fluid then you get a sudden burst of torque as line pressure builds up.
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Originally Posted by cleric670@gmail
(Post 7136689)
Check your AT fluid level, it could be running low on fluid then you get a sudden burst of torque as line pressure builds up.
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What happens when you use a service jack to lift up the vehicle? Do you hear any wierd noise coming from the suspension as you raise it? Maybe indicating something is broken or severely worn.
Also if you have a sunroof equipped are you sure the sound isn't coming from the sunroof? |
Also, take out the trunk floor mat and both plastic dividers and check to make sure everything is securely bolted down like the spare tire/jack/HICAS controller, etc
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Originally Posted by cleric670@gmail
(Post 7136709)
What happens when you use a service jack to lift up the vehicle? Do you hear any wierd noise coming from the suspension as you raise it? Maybe indicating something is broken or severely worn.
Also if you have a sunroof equipped are you sure the sound isn't coming from the sunroof?
Originally Posted by cleric670@gmail
(Post 7136712)
Also, take out the trunk floor mat and both plastic dividers and check to make sure everything is securely bolted down like the spare tire/jack/HICAS controller, etc
It feels as if gears are slipping. It cant be the diff since i swapped it to another one. I dont see how the tranny could be slipping since it doesnt give off erratic downshift or upshift. And still, somehow the rear just goes nuts and starts thudding and shaking the damn car. |
I'd recommend re checking the rear suspension. Maybe your diff bushing is completely screwed?
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Originally Posted by Urbanengineer
(Post 7136721)
I'd recommend re checking the rear suspension. Maybe your diff bushing is completely screwed?
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It sounds like your tranny is about to implode, I'd have it towed somewhere to be looked at. I've been involved in a massive transmission failure in the past and it wasn't a pleasant experience.
I don't know that anything not mechanical could cause the symptoms you are describing and it sounds like you've ruled out the diff. as a potential cause. |
Originally Posted by Blue Dream
(Post 7136746)
It sounds like your tranny is about to implode, I'd have it towed somewhere to be looked at. I've been involved in a massive transmission failure in the past and it wasn't a pleasant experience.
I don't know that anything not mechanical could cause the symptoms you are describing and it sounds like you've ruled out the diff. as a potential cause. |
Added a video to better help hear it. You can hear it a couple of times in the video.
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I definitely think it's the transmission now. To me it sounds like gears are slipping causing the noise and vibration which would also explain the RPM jumps with no power. Then they catch and all is well. It seems the noise is closer to you than an engine issue would be, on my laptop's poor speakers it sounds like something's vibrating right under the floor of the car.
But I'm not an expert and members like cleric have vastly more technical knowledge than I do so I'll stay subscribed to this thread bcuz I'm curious what it turns out to be. I can honestly say that after owning my G for 9 years I've never heard of another G or Z have an issue like what you're going through and over the years I have known/know several hundred G and Z owners.. |
Originally Posted by Blue Dream
(Post 7136760)
I definitely think it's the transmission now. To me it sounds like gears are slipping causing the noise and vibration which would also explain the RPM jumps with no power. Then they catch and all is well. It seems the noise is closer to you than an engine issue would be, on my laptop's poor speakers it sounds like something's vibrating right under the floor of the car.
But I'm not an expert and members like cleric have vastly more technical knowledge than I do so I'll stay subscribed to this thread bcuz I'm curious what it turns out to be. I can honestly say that after owning my G for 9 years I've never heard of another G or Z have an issue like what you're going through and over the years I have known/know several hundred G and Z owners.. |
Lol that is wild. I can't even think of anything on the car that sounds like that. It almost doesn't sound metalic enough to be gears..but it does sound like some fluttering gears.
Hmm..do you have a baseball card in your spokes? |
Originally Posted by ScraggleRock
(Post 7136765)
Lol that is wild. I can't even think of anything on the car that sounds like that. It almost doesn't sound metalic enough to be gears..but it does sound like some fluttering gears.
Hmm..do you have a baseball card in your spokes? I’ll double check on the spokes lol. |
Oh, Snap, that's kind of the same chatter (but more violent) that comes from the ABS a little after you start the car. Wonder if it could be an ABS issue in the rear.
When's the last time you changed youe brake fluid? |
Originally Posted by ScraggleRock
(Post 7136778)
Oh, Snap, that's kind of the same chatter (but more violent) that comes from the ABS a little after you start the car. Wonder if it could be an ABS issue in the rear.
When's the last time you changed youe brake fluid? |
Wow that sounds absolutely terrible... If it wasn't for the rpm flutter I'd say to check the front bolts on the plastic engine bay cover under the vehicle it sounds like something flapping in the wind and slapping the car really hard.
I think youre going to need to take this to a shop asap for a diagnosis before it Kabooms and leaves you stuck on the road. |
So after doing some more digging and self diagnosing, it turns out it’s what’s called a “transmission chatter”. Basically it’s either failed fluid or slipping torque converter clutch because of loss of fluid pressure. Sooooo, it’s either I try to drop the pan, change the filter and drain the fluid out a couple of times, or I just let it die. Not gonna let it die! |
Does anyone know if the pan bolts are reusable? The FSM says it's not but there's no part number listed for the bolts when looking online. :dunno:
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Wow that's funny it DOES say to not reuse transmission bolts, probably the same sort of thing as it saying not to reuse the intake manifold bolts. It's a cheap insurance policy for the dealership against anything potentially happening to the transmission, they have deniability against fastener problems because they used new bolts. I would definitely reuse them without a second though.
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Originally Posted by cleric670@gmail
(Post 7137134)
Wow that's funny it DOES say to not reuse transmission bolts, probably the same sort of thing as it saying not to reuse the intake manifold bolts. It's a cheap insurance policy for the dealership against anything potentially happening to the transmission, they have deniability against fastener problems because they used new bolts. I would definitely reuse them without a second though.
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Nahh the bolts aren't going to leak, you will be using permatex ultra grey on the pan gasket though.
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Originally Posted by cleric670@gmail
(Post 7137138)
Nahh the bolts aren't going to leak, you will be using permatex ultra grey on the pan gasket though.
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Ohhh sorry, I forgot that pan had a gasket.
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Quick update, dropped the pan last week, cleaned it up changed the filter. Filter looked good, but changed it anyway, but boy was the pan dirty. The two magnets had an insane amount of metal shavings, didn’t look too good, fluid was very very dark and had a burnt smell. So dropped the pan, changed the fluid the first time (5 qts). and then did a fluid change over the weekend, 4 qts. Definitely isn’t as violent but still there. Not sure if I should do it again to the point where the atf is pink instead of a brownish pink which it is at the moment. Hmmmmm. |
It's not uncommon for those magnets to pick up a fairly significant amount of debris with 170k on the drivetrain but I have a feeling that unit is going through a pretty quick death cycle and you should start making arrangements for the funeral. The fluid being in that bad of condition means it was probably never maintained and it's a technological miracle that it's survived that long on the original fluid :)
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Originally Posted by cleric670@gmail
(Post 7138196)
It's not uncommon for those magnets to pick up a fairly significant amount of debris with 170k on the drivetrain but I have a feeling that unit is going through a pretty quick death cycle and you should start making arrangements for the funeral. The fluid being in that bad of condition means it was probably never maintained and it's a technological miracle that it's survived that long on the original fluid :)
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You change the fluid regularly and it's still smells/looks burned up? That pretty much means overheat condition due to slipping clutches or brakes, when you disassemble it you'll probably find at least one set of clutch packs that is completely scorched. It's a pretty vicious spiral once that happens, the more breakdown of fluid the faster the clutch/brakes burn up and the faster particulates damage the valve body/torque converter (erosion) which in turn leads to MORE damage...
It wouldn't hurt to drain/fill the fluid one more time because the more particulates you pull out the more you delay the inevitable but if it comes out looking/smelling scorched again with significant debris on the magnet then you should start immediately shopping for a replacement unit. |
Originally Posted by cleric670@gmail
(Post 7138202)
You change the fluid regularly and it's still smells/looks burned up? That pretty much means overheat condition due to slipping clutches or brakes, when you disassemble it you'll probably find at least one set of clutch packs that is completely scorched. It's a pretty vicious spiral once that happens, the more breakdown of fluid the faster the clutch/brakes burn up and the faster particulates damage the valve body/torque converter (erosion) which in turn leads to MORE damage...
It wouldn't hurt to drain/fill the fluid one more time because the more particulates you pull out the more you delay the inevitable but if it comes out looking/smelling scorched again with significant debris on the magnet then you should start immediately shopping for a replacement unit. |
Sounds similar to mine, just more extreme. Mine mostly slipped/made noise when cold, ended up with aluminum in the pan. Only thing aluminum in the transmission is the casing AFAIK, so something was chewing up the inside of the case...it was a pricey fix. Only did it cause (a) car had the packages I wanted and (b) I have plans to build it.
It's a guessing game as to how long you can keep driving, aggressive driving is just going to accelerate it. If the fluid stays clean for a while after a change, you can probably keep driving for a while, but I'd start looking for another ride/cheap transmission... |
Originally Posted by ScraggleRock
(Post 7138254)
Shouldn't he wait like 1000 miles or so, so the detergents have a chance to work stuff out? If he changes it now it'll just be changing new fluid.
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do you guys think its worth rebuilding/replacing the trans? I'm at a dilemma thinking if it's worth putting that in a car with 175k.
i just replaced the damn fluid on monday and the smell is insane. i think i killed it. |
The detergents just prevent sludge from accumulating. The reason I suggest another drain fill immediately is to flush out more of the contaminants. This is one of the rare cases where I think an actual power flush is worth the risk, you have SO MUCH particulates in the fluid that you really need to get them out quickly to prevent more rapid wearing of components.
I still think the transmission is toast though, it will probably start slipping soon if it hasn't already begun to. |
Originally Posted by Genthusiast35
(Post 7138298)
do you guys think its worth rebuilding/replacing the trans? I'm at a dilemma thinking if it's worth putting that in a car with 175k.
i just replaced the damn fluid on monday and the smell is insane. i think i killed it. |
Agreed, I'd just replace it. A rebuild will be pricey and who knows how many miles your car has left in her.
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Alright sounds good. Thanks for the help guys. I really do appreciate it.
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Does anyone know if an 07 trans would fit an 05? I looked up part numbers and they’re completely different but I read somewhere that 05-07 AT trans are interchangeable. Part numbers are throwing me off. |
It's my understanding you should be fine, hopefully cleric or someone else will confirm or deny soon.
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