5 different mechanics, $4,000 in parts, still no answer..

[Carey251]

Good Morning,

Something that came to mind, a couple months back, my remote start stopped working as a result of my check engine light coming on. I went to the auto shop that date and my throttle position sensor as well as my oil pressure sensor were both dead.

Does anyone know what would cause both sensors to go out at the exact same time? I would imagine it is electrical related? I check all the fuses and did not find a blown fuse. Any other suggestions as to what would cause these to both stop working?

 

[swathdiver]

Purely a coincidence or theft. Don't your trucks also have two TPS sensors like the GMT900s?

 

[Eismann95]

I'm having the same issue with my 08 Denali XL. Just had a new trans put in last summer, so it's not that. Thought it may be tire noise, but that wouldn't explain the noise stopping when lifting off the accelerator. Seems as though my issues is intermittent, as it doesn't happen all the time when going over 50. Thought it may be a hub, but haven't dug into that because it's too damn cold to go into the non-heated garage to do the work.

 

[Geojarn]

Could be bearings on alternator, happened on my pontiac.

 

[Charles Land]

Good Morning Everyone,

First time posting here. I have come out of desperation for a mechanical issue that no mechanic seems to be able to identify.

I drive a 2008 Tahoe LTZ 2WD, with about 100k miles. Over the last year, the vehicle has been making a whirring noise that has progressively gotten worse. The whirring noise only happens when driving up over 50-55 MPH, and when on the gas. The whirring noise goes away almost instantly when I let off and then comes back on again when I tap the accelerator. The noise seems to be the worse when I am driving on the free, up slight inclines, and when I let off the accelerator, and then tap the accelerator again.

To date, I have been to 5 different mechanics, all seem to think it is coming from the transmission or differential, but at this point, I have replaced nearly every part in both.

This far I have replaced:
-rear wheel bearings
-all new bearings in the rear differential, including the pinion bearing (a few mechanics were certain it was the pinion bearing).
-had the transmission rebuilt
-had a new pinion and ring installed (pinion was worn down a bit and wasn't in great shape)

After seeing the pinion, I was certain I finally had it fixed and it didn't make the noise while driving the next day after replacement. However, the second day after it was replaced, the noise was back and almost just as bad.

Everyone thinks it is drive train related but it sounds like it is coming more from the front portion of the car. It really sounds like a bad front wheel bearing, but it wouldn't make sense, as it only happens at high speed, when on the gas, and goes away almost as soon as I let off the accelerator.

Has anyone heard of a problem similar to this? My Tahoe is in immaculate shape, I would hate to trade it in, but at this rate, I am close to giving up.

Any input is greatly appreciated!

Thanks!

Good Morning Everyone,

First time posting here. I have come out of desperation for a mechanical issue that no mechanic seems to be able to identify.

I drive a 2008 Tahoe LTZ 2WD, with about 100k miles. Over the last year, the vehicle has been making a whirring noise that has progressively gotten worse. The whirring noise only happens when driving up over 50-55 MPH, and when on the gas. The whirring noise goes away almost instantly when I let off and then comes back on again when I tap the accelerator. The noise seems to be the worse when I am driving on the free, up slight inclines, and when I let off the accelerator, and then tap the accelerator again.

To date, I have been to 5 different mechanics, all seem to think it is coming from the transmission or differential, but at this point, I have replaced nearly every part in both.

This far I have replaced:
-rear wheel bearings
-all new bearings in the rear differential, including the pinion bearing (a few mechanics were certain it was the pinion bearing).
-had the transmission rebuilt
-had a new pinion and ring installed (pinion was worn down a bit and wasn't in great shape)

After seeing the pinion, I was certain I finally had it fixed and it didn't make the noise while driving the next day after replacement. However, the second day after it was replaced, the noise was back and almost just as bad.

Everyone thinks it is drive train related but it sounds like it is coming more from the front portion of the car. It really sounds like a bad front wheel bearing, but it wouldn't make sense, as it only happens at high speed, when on the gas, and goes away almost as soon as I let off the accelerator.

Has anyone heard of a problem similar to this? My Tahoe is in immaculate shape, I would hate to trade it in, but at this rate, I am close to giving up.

Any input is greatly appreciated!

Thanks!

I had those symptoms on a 2001 Suburban - it was one of the drive shaft universal joint bearings.

 

[jackD]

What about u joints?

Bent driveshaft?

The fact that it’s literally loaded vs unloaded on acceleration etc it’s the differential and where you need to focus.

A cheaper option is buying a used differential.

Have you tried indexing the driveshaft and see if it helps?

 

[gpd4]

My 2007 Sub has almost the same symptoms. Transmission and rear end were replaced within the last 6 months (182K miles now). Last time I had it looked at, the shop found a broken motor mount and that helped with the noise a little, but it's definitely not gone. He suggested tires, but the noise didn't change at all after rotating them. Mine is 4WD, so I'm really hoping it's not the front diff. Will probably do front wheel bearings after it thaws here...but after reading this, I'll definitely check the UJoints as well.

 

[Big Mama]

Silly of me to ask but I didn’t see where anyone asked about any vacuum leaks near the area? As y’all know they are worse when cold and could be as simple as the hose was removed and put back on when job was done when noise went away. If the “Whirr” you’re talking about isn’t air noise but mechanical disregard. Vacuum always sounds worse when on the gas. I’m not sure which lines are near the noise but it’s free and easy to check. Good luck and sorry about the problem.

 

[Chubbs]

Sorry for the confusion, that is correct, this is a 2WD, so no front differential to consider.

I haven't had anyone look at the front of the car yet because all of the rides I have gone on with the mechanics made them certain it was an issue in the rear of the car. I will jack it up and test to see if the wheels spin freely on each side.

Yesterday, I did notice this when I got home from work and popped the hood. I am not an expert by any means, is this a leaking oil cooler? I have not noticed this before. It looks like I have lost a fair amount of oil through this hose.

View attachment 192423

have you not been regularly checking the fill level of the various systems?

is this leak you pointed-out puddling on the ground?

make sure all of your fluids are topped-off and remain so before you go chasing your tail LOL

failing driveshaft u-joints always make a sound but that doesn't explain the noise subsiding after parts replacement, then picking up where it left off a day or 2 later.

other than a low-fluid condition being the cause of a sound..

if there was a pinion bearing failure, it could be caused by something weird like an unbalanced drive shaft or a failed output bearing of the transmission, you know where the driveline is distorted. just throwing that out there.

 

[Sone217]

I don’t know if this be of any help. I have a 2007 escalade AWD. I had the same issue as you describe. I had done the u joints to no success. Until finally the transfer case went, wasn’t expecting for the noise to be gone but voila! Took it on the highway and guess what she was sound as new. Might wanna check that transfer case out if you have 4x4.