2011 Impala LT 3.5 mystery noise

Seif

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Hello all,
First time post here and first Impala (2011 LT, 3.5, Luxury package I think they called it) but I really love it. Thanks in advance for any help as I'm at a loss on this issue. I'm an almost 60 year old kid, can do basic auto repair, and I tend to try to find a screaming deal on a 100k miles or so mid-full size American car every few years, spruce up, drive to 150-175k, and repeat. Bought this one about 6 mos ago with 100k on it and except fixing for minor stuff (blend flap actuator clicking, etc.) She has been great. Recently I noticed a substantial whine (kinda like a diesel pickup turbo whine but not as loud) and here are the details:
"Not throwing any codes. Whine is only in gear, no noise in park/neutral, matches rpm, thought maybe alternator, battery was 5 yr old mid price Wal-Mart so replaced but no change in noise, no noise when in park turning steering wheel, no noticeable leaks, temperature is perfect, no idiot lights, shifts perfectly, runs/drives perfectly. No other noises. Thought torque converter but it shows no symptoms of TC issues. Changed out about 6 quarts of trans fluid with correct (expensive) full synthetic trans fluid, (just pumped out and replaced) but no change in noise.". Was going to add a bottle of Bars leak high mileage trans additive but have not yet. In park, compressor on or off no noise, and noise does not change in gear with compressor on or off.
One mechanic put a stethoscope on it and said upper idler pulley. I thought it was a stretch (no noise in neutral/park) but I figured it could use a serpentine belt so I replaced both. No luck.
I saw one post that said "No sound in neutral? Does it vary with steering? If it goes away in neutral and isn't affected by steering, its just a noisy transmission oil pump, common issue that doesn't really hurt anything.". Could that be the case? Just keep driving till something else changes? I have also seen clogged/old trans fluid filter can create noise from the pump. I need to drive about 450 miles to visit my elderly uncle but should I trust it? (Otherwise it is 95% local driving) Breaking down between here and there is a bad thought.
Again thanks very much for the help! I hope I can pay it back sometime!
(Please also let me know if I need to post elsewhere in the forum)
Seif
 

zora

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If you put the vehicle in drive, place your left foot solidly on the brake and with your right foot give it some gas, do you hear the noise?
Do you only hear the noise while the vehicle is moving?
If so have you shifted into neutral while hearing the noise to see if it stops?
 

Seif

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If you put the vehicle in drive, place your left foot solidly on the brake and with your right foot give it some gas, do you hear the noise?
Do you only hear the noise while the vehicle is moving?
If so have you shifted into neutral while hearing the noise to see if it stops?
Thank you very much for the reply Zora. Yes, foot on brake in gear, noise is there, whine pitch goes up as RPMs increase. Same while driving. No noise in neutral whether the car is moving or not. It is a very similar noise to that I have heard in videos from idler pulley bearings worn out but that would be neutral or in gear right? Would any of the 9 pulleys on the serpentine belt make noise ONLY while in gear? (I have not put stethoscope/screwdriver to all 9) If not, I'm thinking maybe dropping the pan and changing potentially clogged/dirty trans fluid filter and fluid would be my next step?
 

zora

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With a trusted assistant and the wheels blocked have them put the car in drive, foot on brake, parking brake applied, and step on gas to generate noise. You use a stethoscope to locate the noise.
 

Seif

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Thanks much again Zora. To be clear can you tell me what pulleys/accessories would make zero noise in park/neutral even revving the engine, and make the whining noise that goes up in pitch with RPMs while in gear?
 

zora

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Doesnt make sense that any of them would be effected by whether the car is in park or gear, they would always be noisy.
 

Seif

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That's kinda what I was thinking. This is unmistakably obvious noise (whine) in gear, zero noise out of gear. But no shifting issues. That's why I don't think TC issues, but I have seen that a trans oil/fluid pump may be going bad or is starved for fluid (?) and making noise due to filter clogged. I might as well blow another hundred and change the fluid again but this time do it via dropping the pan (instead of pumping out) and change the filter. Better than 1k or better to get to and replace the front pump which I cannot do myself. I'll take any other ideas you might have and thanks again so far!
 

zora

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I missed the part about changing the fluid without changing the filter.
Did you have the noise before you changed only the fluid?
 

Seif

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I missed the part about changing the fluid without changing the filter.
Did you have the noise before you changed only the fluid?
Yep. After noise started, and fluid looked not quite acceptable to me right at 100k miles, (just not quite clear and red, a little dark) I decided to do the pump out and replace most of it with good quality correct synthetic. But sadly no change in noise. Previously for my last several cars, I would always leave trans fluid alone if it looked ok after 100k miles and no issues. Let that sleeping dog lie. And no flushes, ever. But I was (am) desperate to do what I can to potentially save this tranny that may be ailing. Ideas?
 

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Thanks much anyway for your replies Zora. You seem to be the only one brave enough to even offer an opinion!
 

zora

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Having people to try and diagnose a noise over the internet, even with a video, is extremely difficult. It requires a hands on first person approach.
 

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Well I have now pumped out all fluid, dropped the pan and replaced the transmission fluid filter because I saw that a clogged filter might make the pump whine, no excessive metal on the magnet, and put back a gallon of the old fluid (since it was fresh/mix) and filled the rest of the way with new. No change in noise, still shifts fine. Anybody have ideas?
 

zora

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Since you only hear it in gear, even when not moving, it appears to be internal to the transmission. You can try a transmission shop to see if they agree and if they consider it a indication of a potential failure.
 
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