Soft knocking noise

848 Views 14 Replies 5 Participants Last post by RocketSled, 7 mo ago

NorCalV

Discussion Starter · 7 mo ago

Hey guys first post here.
Just bought a 09 V and noticed there is a slight knocking noise when you start to take off. I can feel it slightly in the shifter to. Once I am driving I don't notice is at all and it's only when I start taking off. I did do a search and only fond it could be the carrier bearing or diff. I just changed the diff fluid and it was really nasty and I even turned the wheels by hand to see if I can feel if there is anything in the axles or hear it.

I am also having a push pull feeling once in a while but I am thinking that's because the brakes are badly worn and the rotors even have a lip on them

.

So basically asking if that the knocking noise could be the bearing of should I look elsewhere? It's hard to see the bearing with that dang heat shield there 🤦‍♂️

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kittyboy

· #2 · 7 mo ago

Could be a lot of things, to include 'normal' operation. Is it manual or auto? If manual, the transmission does have a normal bit of what's defined as 'gear rattle.' The input shaft gear reverberates through the clutch plates, depending on what clutch you have installed, different levels of sound and feel occur.

I'd suggest if you just bought the car, you or some other experienced mechanic should perform a very in depth inspection, to include borescope cylinders and valves, compression test, etc... Also, if it's been tuned, re-verify the tune for any lean areas. Really, just thoroughly go thru everything. For sure replace ALL fluids, to include the rear diff. When draining the fluids, filter them through white paper towels to observe any signs of metal.

Start keeping a journal, if you're like EVERYONE on this sight, you're now on a path to never ending maintenance/repair/modifications! If your married, start training early. Your wife needs to understand and embrace car parts as a good thing.

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Reactions: 1

MrSurly

· #3 · 7 mo ago

Auto or stick? Make the noise when not moving? In neutral? On decell? At cruise?
Sound seems to emanate from what area?
Is the frequency of the knock related to engine speed/driveshaft speed/ road speed?
Does the noise stop when you take any action? Turning? Braking?
There may be more questions.

Reactions: 1

NorCalV

Discussion Starter · #4 · 7 mo ago

kittyboy said:
Could be a lot of things, to include 'normal' operation. Is it manual or auto? If manual, the transmission does have a normal bit of what's defined as 'gear rattle.' The input shaft gear reverberates through the clutch plates, depending on what clutch you have installed, different levels of sound and feel occur.

I'd suggest if you just bought the car, you or some other experienced mechanic should perform a very in depth inspection, to include borescope cylinders and valves, compression test, etc... Also, if it's been tuned, re-verify the tune for any lean areas. Really, just thoroughly go thru everything. For sure replace ALL fluids, to include the rear diff. When draining the fluids, filter them through white paper towels to observe any signs of metal.

Start keeping a journal, if you're like EVERYONE on this sight, you're now on a path to never ending maintenance/repair/modifications! If your married, start training early. Your wife needs to understand and embrace car parts as a good thing.

Sorry forgot to mention it's a auto. It is a one owner car and runs amazing besides one injector failing which I replaced and soon will replace with better injectors when funds allow. I changed the fluids in the diff, trans and motor already. Searched here on how to drain and replace the trans fluid and added the 1 extra quart. She does shift a bit smoother now.
I am not shy of working on cars and doing repairs on them at all and shockingly my wife is ok with it and knows it helps me relax. This is my first GM car so I am learning the way lol.

kittyboy

· #5 · 7 mo ago

NorCalV said:
Sorry forgot to mention it's a auto. It is a one owner car and runs amazing besides one injector failing which I replaced and soon will replace with better injectors when funds allow. I changed the fluids in the diff, trans and motor already. Searched here on how to drain and replace the trans fluid and added the 1 extra quart. She does shift a bit smoother now.
I am not shy of working on cars and doing repairs on them at all and shockingly my wife is ok with it and knows it helps me relax. This is my first GM car so I am learning the way lol.

I'm glad you find it relaxing, need to hook-up with duck and teach him some breathing exercises. haha

I like GM overall, nothing in life is perfect. I always make sure to purchase parts directly from authorized GM dealers when replacing stock parts. These days there are too many counterfeit copies on line.

Reactions: 1

NorCalV

Discussion Starter · #6 · 7 mo ago

MrSurly said:
Auto or stick? Make the noise when not moving? In neutral? On decell? At cruise?
Sound seems to emanate from what area?
Is the frequency of the knock related to engine speed/driveshaft speed/ road speed?
Does the noise stop when you take any action? Turning? Braking?
There may be more questions.

It's a auto and no noise when sitting still or neutral. I mainly hear it when I take off but then it seems like it goes away and I just hear the exhaust then. It does speed up when I get going from a stop. Not sure where but my wife says it sounds like the middle of the car or the rear. I put my hand on the floor in the back and can feel it then also. When I let off throttle I can hear it very faint.

It did make a louder pop or knock noise the other day when turning into my daughters school and made me think the rear axles possibly but they "look" to be in great shape and didn't feel anything when I was turning them by hand.

I am going to try and see if I can get a video of it or put it back on the stands in the morning and put it in gear and get under and see if I can hear anything.

kittyboy said:
I'm glad you find it relaxing, need to hook-up with duck and teach him some breathing exercises. haha

I like GM overall, nothing in life is perfect. I always make sure to purchase parts directly from authorized GM dealers when replacing stock parts. These days there are too many counterfeit copies on line.

It takes a lot to keep me relaxed while working on my cars but usually take my sweet time and crank the tunes and maybe have a beer break in between helps lol!

I agree nothing is perfect and I knew this car would need a little love since she's older. First GM car and I am really liking it. I am coming from a 12 Chrysler 300 SRT8 that got totaled 3 weeks ago from a moron

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iviaillet

· #7 · 7 mo ago

kittyboy said:
I'm glad you find it relaxing, need to hook-up with duck and teach him some breathing exercises. haha

I like GM overall, nothing in life is perfect. I always make sure to purchase parts directly from authorized GM dealers when replacing stock parts. These days there are too many counterfeit copies on line.

How do you feel about GM genuine parts from rockauto?

MrSurly

· #8 · 7 mo ago

You said you just changed the diff fluid.
What fluid did you use and did you add the required friction modifier?
Does the noise occur only when turning? Even slightly turning?

The limited slip can pop a lot if it does not have the friction modifier but only when the two axles are rotating at different speeds. Which normally only happens when turning, however, if the two rear tires are different diameters… it happens all the time.
Since you just got the car, you should verify the tire sizes.

NorCalV

Discussion Starter · #9 · 7 mo ago

MrSurly said:
You said you just changed the diff fluid.
What fluid did you use and did you add the required friction modifier?
Does the noise occur only when turning? Even slightly turning?

The limited slip can pop a lot if it does not have the friction modifier but only when the two axles are rotating at different speeds. Which normally only happens when turning, however, if the two rear tires are different diameters… it happens all the time.
Since you just got the car, you should verify the tire sizes.

Tire sizes are the same. I put in Lucas 75-90 and no modifier. I was trying to see if it needed it when I was there but the bottle said it's not needed and it's already in it but I will go tomorrow and get it to be safe.

The pop was only once when I turned into the school and was a sharper turn. Haven't heard it when slightly turning yet. Only noise I constantly hear is the faint knocking noise when I start driving and increases with speed but then get drowned out by the road noise and exhaust.

I was reading more today seeing that the bearing is the same as the base cts and was thinking of getting it but from what I read it's a pain to sepreate the two shafts

MrSurly

· #10 · 7 mo ago

The carrier bearing would certainly be suspect. If the Lucas contains the modifier, there’s nothing to be gained adding more.

NorCalV

Discussion Starter · #11 · 7 mo ago

MrSurly said:
The carrier bearing would certainly be suspect. If the Lucas contains the modifier, there’s nothing to be gained adding more.

I was thinking that but I will read the bottle again to make sure. Always good to double and triple check.
Has anyone separated the driveshafts here on their own? I searched and didn't see a DIY or any me tion besides sending them out

kittyboy

· #12 · 7 mo ago

Don't think it is a good idea to mix the modifier with other brands of oil. To answer your question, like I said, I buy all my stock replacement parts from authorized GM dealers.

RocketSled

· #13 · 7 mo ago

Soft, repetitive knocking = Bad CV/Universal joint in the drive line.

NorCalV

Discussion Starter · #14 · 7 mo ago

RocketSled said:
Soft, repetitive knocking = Bad CV/Universal joint in the drive line.

Guess I need to find axles and a driveshaft to be on the safe side. I did look at the driveshaft and the Joint from what I could see looks good but I'm sure that isn't a good way to tell by looking between the heat shield.

RocketSled

· #15 · 7 mo ago

No. The Universal Joints on the drive shaft are visible, but the Constant Velocity couplings in the axle half shafts are packed in grease inside rubber boots and not visible. Also, you can't really tell if a Universal or CV is bad just by looking (unless it's really bad), you need to actually twist them and see how much lash they have, or if they're sticking at some point in their revolution.

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