Car makes a noise like somebody is hitting it with a hammer from underneath.

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rocker69
Posts: 4
Joined: Mon Oct 27, 2014 6:43 pm

Car makes a noise like somebody is hitting it with a hammer from underneath.

Post by rocker69 »

I have a 2005 Pontiac vibe auto transmission. Some idiot ran a light and I had to slam on my brakes as hard as I could. I heard a huge snap when I did and the car made a noise like somebody was underneath it hitting it with a huge hammer. This happened again when I accelerated quickly and again when I had put the car in reverse. It seems to have worked itself out. I just replaced the front and rear motor mounts because I thought that I just snapped a motor mount. I think it was more than that now. Does anyone have any idea what might have been the problem? Did my transmission disengage from the engine? Any ideas what would make that sound?
Last edited by rocker69 on Mon May 09, 2022 3:03 pm, edited 1 time in total.
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joatmon
Posts: 9710
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: Car makes a noise like somebody is hitting it with a hammer from underneath.

Post by joatmon »

I see from your other posts you have a 2005 base Vibe, I assume auto tranny.

Regarding the hammering sound, does it seem to track the engine speed or the vehicle speed?

What do you mean by " It seems to have worked itself out."? Did the problem go away?

My first guess given the snap when you hit the brakes hard would be to check out the brakes
rocker69
Posts: 4
Joined: Mon Oct 27, 2014 6:43 pm

Re: Car makes a noise like somebody is hitting it with a hammer from underneath.

Post by rocker69 »

Yes the knocking did just go away. Brakes are good. Just changed the pads it wasn't timed with the speed or anything like that. It would just go bang bang bang bang. Like one second after another. Would the front drivetrain have maybe popped out and then slipped back in? I mean where the motor and or transmission would connect to the two front wheels. The banging noise happened right around the firewall from the bottom of the car. Or at least it sounded like it was directly under my feet.
SSizler
Posts: 72
Joined: Tue Jan 21, 2020 7:06 pm
Location: Urbandale, Iowa

Re: Car makes a noise like somebody is hitting it with a hammer from underneath.

Post by SSizler »

Sounds like you are describing the ABS modulating during a hard stop.
2003 Vibe Base / Frosty Mono / Moon & Tunes / Auto / Well equipped / 200k mi
2006 Vibe AWD / Lava Red Mono / Loaded w/Leather and Sport Pkg / 141k mi
Many other 2 & 4 wheel toys :mrgreen:
39 years with a wonderful woman / 2 adult kids
andrewclaus
Posts: 395
Joined: Tue Oct 03, 2017 6:38 pm
Location: Golden, CO

Re: Car makes a noise like somebody is hitting it with a hammer from underneath.

Post by andrewclaus »

Check suspension and steering components like the lower control arms, ball joints, struts.
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