weird "thud" sound - NJFBOA - Home of New Jersey's Camaros and Firebirds

NightRydaSS · 04-02-2007, 11:06 AM

Ugh, got another one for you guys: Everyone once in a while when i put the car in reverse (manual Trans) or in 1st after it has been sitting for a lil bit i hear a slight "thump/thud" in that back of my car. it sounds like it is coming from my rear end.

I have NO vibrations at highway speed. No banging, clanging, rattling, ect; the car drives perfectly fine and shifts perfectly fine. I dont always get this sound either. Normaly it is when the car has been sitting for a bit. Example, last night i was a Fudruckers in Washington Township for a lil cruse in. i have backed my car in to a parking spot and let it site for about 45 mins. When i pulled out i heard a lil "thud" coming from my rear. The car shifts gears fine, just when the cars started to move, i heard a "thud", I also heard the same sound when i backed outa my drive way this morning. It NEVER happens stopped at a light, and i tried to recreate the issue last night at a school parking lot and what only able to do it once.

The only thing i did was install Bliestin shocks on it 2weekends ago. i jacked the car up from under the punpkin (the center of it as to not crack the cover or anything), and was carful not to put it on the drive shaft or TQ Arm. i find it hard to believe that harder shocks wuold be so sensitive that im picking up road bumps when i'm hardly moving move. I asked my dad and he said my u-joint might be going bad from banging gears in my car, that this happens, but wouldn't i always have this sound if that was the case? Could my u-joint be going bad?

is there a way to check my drive shaft or my u-joint to see if it is going bad or if my drive shaft is outa wack? i can't really do anyting about this until it is a consistant issue, it is just werid now.

thanks for any help guys!

SamhainZ28 · 04-02-2007, 11:11 AM

does the thump sound like it coming from the tranny like right in the middle of the car more so than the rear? because it sounds like a broken tranny mount to me, but i could be wrong

Tru2Chevy · 04-02-2007, 11:20 AM

A broken tranny mount would most likely start making all kinds of noise every time you grabbed a gear while accelerating.

I would get under the car and inspect the rear u joint and the caps that hold it to the rear yolk.

- Justin

NightRydaSS · 04-02-2007, 12:06 PM

I thought about the tranny mount, but i remembered when i had my the Trans Am and my mom broke the mount, it rattled all the tme. The best i can describe the location is it sounds like it is coming from under where you would put the t-tops when u take them off. However, i did feel it behind my seat before one.

bobb1589 · 04-04-2007, 04:42 AM

i think i am experiencing somewhat of the same "thud" you are. the problem is that it is not always a constant thing so when i go to show someone of course everything runs perfect

NightRydaSS · 04-04-2007, 10:58 PM

yea i kno, it isn't consistant or always there. the ONLY time i have noticed this "thud" is when i put my car in reverse to pull out of where it is parked, or i put in it 1st to pull away from where it is parked. And it DOESN'T do it all the time. It DOESN'T happen stopped at a light while i take off, and there are no vibrations, rattles, clings/clangs, grinding, or ect coming from the drivetrain while driving (you would think it would make it's pressence known when the car is moving). AND i can't always recreate it, it seems to only happen after the car has been sitting.

It sounds like it is coming from my rear diff, but, wouldn't there always be an "out of place sound" when the car moves it if were the diff? If it were the drive shaft, wouldn't it be worse while driving especially at highway speeds?

My dad suggests it is my u-joint going bad, but what r the symptons of that? Or symptons of one GOING bad?

I guess im just paranoid. I mean i don't have an issue with waiting till there is a "real issue", but on the other hand i dont want my rear diff to blow the ***** up or my driveshaft to fall out. I just want to find out if this is a warning sign for something going bad.

bobb1589 · 04-06-2007, 09:45 PM

i am in the same situation... its hard to tell what the f*** it is and then when you go and ttry to show someone you cant get it to do it... i even had my friend drive aroudn and he said he felt nothing... maybe we are just paranoid

NightRydaSS · 04-23-2007, 01:50 PM

Well, i gave my cousin a call (the Chevy mechanic one) and told him what i was experencing. He said that the new '07 Avalanches have the same issues. It has to do with the hollow/aluminum drive shafts transfering sound through the drive train (i think).

i asked him about my U-Joints and told him that i don't hear/feel any grinding, vibrating, banging, ect while driving on the highway (where it would be most noticeable). he said that b/c i have 81K miles on her, it could just be the age of the car making noise and what-not and they COULD be wearing out. I told him i went under the car and looked at the rear U-Joint and it has no play, and looked at the front U-Joint (into the tranny) and it had only the slightest play. He told me that there is a "play" tolerance that is spec'd for these cars and i might be at the end of that spectrum.

Bottom line he said not to worry now. if it is my u-Joint going bad he said it isn't bad enough to have to fix it, and that it would get a whole lot worse if it was (to the point that there would be no question if there was something wrong) before it broke off. he said it could just be the age of the car, combined with this being my first 6-speed and me never really noticing it b/c i thought that it was a normal sound (i kno when i engage/dis-engage my clutch the drive train catches; aka a kind of "shift shock"), and the only reason y i noticed it now was b/c i was working back there when i replaced my shocks.

I was told to just keep an eye on it and not to worry about it. That is good enough for me, if he doesn't seem worried, then I'm not, and he knew exactly what i was talkin about. he is like an encyclopedia for cars. lol

Knipps · 04-23-2007, 02:05 PM

Quote:

Originally Posted by NightRydaSS

Well, i gave my cousin a call (the Chevy mechanic one) and told him what i was experencing. He said that the new '07 Avalanches have the same issues. It has to do with the hollow/aluminum drive shafts transfering sound through the drive train (i think).

i asked him about my U-Joints and told him that i don't hear/feel any grinding, vibrating, banging, ect while driving on the highway (where it would be most noticeable). he said that b/c i have 81K miles on her, it could just be the age of the car making noise and what-not and they COULD be wearing out. I told him i went under the car and looked at the rear U-Joint and it has no play, and looked at the front U-Joint (into the tranny) and it had only the slightest play. He told me that there is a "play" tolerance that is spec'd for these cars and i might be at the end of that spectrum.

Bottom line he said not to worry now. if it is my u-Joint going bad he said it isn't bad enough to have to fix it, and that it would get a whole lot worse if it was (to the point that there would be no question if there was something wrong) before it broke off. he said it could just be the age of the car, combined with this being my first 6-speed and me never really noticing it b/c i thought that it was a normal sound (i kno when i engage/dis-engage my clutch the drive train catches; aka a kind of "shift shock"), and the only reason y i noticed it now was b/c i was working back there when i replaced my shocks.

I was told to just keep an eye on it and not to worry about it. That is good enough for me, if he doesn't seem worried, then I'm not, and he knew exactly what i was talkin about. he is like an encyclopedia for cars. lol

introduce him to the site, we could always use more knowledge

johnjzjz · 04-24-2007, 08:20 AM

put the e brake on, and with the car in neutral twist the drive shaft back and forth - the shaft moves and you will hear a clunk both ways when rotating - its a wear issue the axle splines have some the carrier has some the spider gears and the ring to pinion all together lots of play -- changing oils might help at some point if they were lighter in the #s instead of 75 / 140 diff you put 75 / 90 but its not really going to do anything -- its normal --- shimming the ring gear might help but also might cause a noise forget about it until you get noises -- for some reason cold oil sends sound different ( muffled ) than hot oil --- thats what you are hearing --- jz