Squeal from Engine/Trans?

[winterismyseason]

Hi guys,
I was hoping someone could help me out. I did some cursory searching on here, but haven't found anything so now I'm asking.

I've got a 2015 Tahoe (85k) which I picked up about 10k miles ago. When the engine and trans are warm, during/after 4 wheeling, backing a trailer up my driveway hill, other load intensive activities, I get a squeal from the back of the engine/transmission area. With the transmission at operating temp, the fluid level looks a little high and the fluid looks relatively clean (hopefully from regular maintenance by the PO).

I only notice this while stopped (in any gear) or moving slowly. It's not super loud, so I'm not sure if it's still happening while driving, but it is easily audible while stopped with the windows up. I've been asked several times what the noise is.

My gut instinct was the transmission, but I'm unsure what would be squealing. Any assistance would be great! Cheers

 

[OR VietVet]

Welcome to the forum from Oregon.

Can you post a video of the noise?


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[Big Mama]

A video would be great. Have you been under it to check trans mount and any loose hardware?

 

[winterismyseason]

Thanks for the replies! Video is uploading, but my internet is struggling tonight. Hopefully the link will work after it's uploaded.

Welcome to the forum from Oregon.

Can you post a video of the noise?


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

I'll follow up this post with the RPO codes and a link to the video

Upgrades/Mods: HID low beams, Fumoto oil valve for clean oil changes, removed the 3rd row seats, added some window vent things. Originally came with 20" wheels, but I replaced them with 18" take offs from a 2020 silverado. Added stock roof rack cross bars. I've thought about plenty more, but haven't pulled the trigger.

Maintenance: Oil changes @5K, acdelco PF63 (not e) oil filter. Tire rotation.

I purchased it back in January, and remember hearing the noise after backing my trailer up my steep driveway the first time. Not sure if the problem was pre-existing. It's a non-issue if there's very little load or if things are cool. Doesn't sound like it's coming from the accessory belts up front, I'm happy to answer any more questions you guys have.

Thanks for the help!

 

[winterismyseason]

RPO Codes:

Video:

Let me know if there's any other info you need!

 

[winterismyseason]

A video would be great. Have you been under it to check trans mount and any loose hardware?

Felt around, Couldn't see anything loose or movable.

 

[Big Mama]

Was the squealing sound going on? I don’t think I heard it. Speaking of belts do you know when they were changed? Everything under your rig looks great. No oil no leaks.

 

[winterismyseason]

Was the squealing sound going on? I don’t think I heard it. Speaking of belts do you know when they were changed? Everything under your rig looks great. No oil no leaks.

Yes. At about 8 seconds in the video (as soon as I get under) you can hear the squeal. It's pretty high pitched though.

While taking the video it sounds like it's coming from the back/bottom of the engine. I may have to poke around with a tube or something to pick up a more precise location.

Not sure when the belts were replaced, but I can barely hear it from the top/front of the engine

 

[Big Mama]

Ok let’s invite some more help. @PNW VietVet @swathdiver @iamdub @Doubeleive @Joseph Garcia and more

 

[Doubeleive]

I watched the video earlier not really sure my best guess is a line under pressure making noise or a pump, maybe pull that transmission thermostat out, do the bypass mod on it and see if that makes any difference it wont hurt anything to try that. easy to do.

 

[swathdiver]

Was able to hear it only when the camera was between the engine and transmission. I'm at a loss to know what it might be though. I reckon something is rubbing at a slower pace then engine rpms. If so, what turns slower then the motor while the motor is on and the vehicle is stationary?

 

[OR VietVet]

My best guess is either a vacuum leak near the back of engine, have heard all kinds of leak-pitches in noise levels-over the years or the dreaded squeal from the rear main seal crankshaft rub or the front trans pump to torque converter seal rub noise. Does the noise pitch change when in gear or neutral or park? Does engine load change it, like with a/c on?

 

[winterismyseason]

I watched the video earlier not really sure my best guess is a line under pressure making noise or a pump, maybe pull that transmission thermostat out, do the bypass mod on it and see if that makes any difference it wont hurt anything to try that. easy to do.

I'll wait a little bit before doing the mod, but I'll do some research to see what's involved.

My best guess is either a vacuum leak near the back of engine, have heard all kinds of leak-pitches in noise levels-over the years or the dreaded squeal from the rear main seal crankshaft rub or the front trans pump to torque converter seal rub noise. Does the noise pitch change when in gear or neutral or park? Does engine load change it, like with a/c on?

Learned something while testing this out. First the results. No change with engine load in different gears (P,N,R), or with A/C on/off. Same pitch and volume. What I did find was that increasing RPM off of idle eliminated the squeal. As soon as idle returned, the squeal returned. Hopefully that's helpful.

Next time I get it warm, I'll crawl under and try to do a little better locating of the sound. I'll poke around and see if I can't find a hose that makes the sound change.

Thanks for the help guys!

 

[Big Mama]

That somewhat leans towards Ron’s idea of a vacuum leak possibly a cracked or even a partially clogged line. Chase, to confirm, there are no dash lights or performance issues, correct?

 

[winterismyseason]

That somewhat leans towards Ron’s idea of a vacuum leak possibly a cracked or even a partially clogged line. Chase, to confirm, there are no dash lights or performance issues, correct?

Confirmed, no dash lights or performance issues. Everything mechanically (besides this sound) seems solid.

Regarding performance, and I think it's intrinsic in these, but around 45-55 on flat roads it doesn't have enough torque to pull 6th gear with only 4 cylinders running and will hunt between 4 and 8 cylinders and what I perceive as locking and unlocking the torque converter.

 

[Joseph Garcia]

Unfortunately, I cannot offer anything on this issue beyond what the other folks have suggested.

Am I correct in seeing the starter come into view early in the video, when the noise is the loudest? Is it possible that the spring-loaded starter solenoid gear is not disengaging, once the motor starts?

 

[OR VietVet]

You need a mechanic's stethoscope to help pinpoint the area where noise is from. They are inexpensive and a must for finding noises.

 

[winterismyseason]

Am I correct in seeing the starter come into view early in the video, when the noise is the loudest? Is it possible that the spring-loaded starter solenoid gear is not disengaging, once the motor starts?

I think that's the starter. While poking around with my new stethoscope this evening, I searched that area pretty well, no luck.

You need a mechanic's stethoscope to help pinpoint the area where noise is from. They are inexpensive and a must for finding noises.

Picked one up today. What an amazing little diagnostic tool. Unfortunately I was unable to locate the source. I poked around for quite awhile with no luck.

I feel like I was able to rule out the transmission, although I did notice for the first time that the transmission crossmember is not original to the truck (probably a red herring for this issue). It doesn't have the same waxy undercoat as everywhere else. (undercoat is covered in sand and silt from a couple remote camping trips in southern Utah, not rusty).


I also noticed the trans support has some musical notes... It's off topic, but still interesting.


The more time I spend under the truck while it's squealing, the further forward I think it may be. I'll have to drop the plastic skid pan and do some more stethoscope-ing this weekend. I'll update with results.

 

[mikeyss]

It throws me off that the noise is only under the trans, but not from up top of the engine. To me, it sounds belt/tensioner related until you stood by that area and the noise is gone. I am guessing a vacuum leak, especially since the vacuum pump is on the driver's side where I hear it the most from your video.

 

[Big Mama]

Once the bottom cover is off you may find that the sound is kind of bouncing around all that metal and is coming from a tensioner or AC