2015 Tahoe LTZ - problem diagnosis

[2015LTZ]

Hello everyone,

A newbie here but I've found a lot of answers to some common problem from this forum.
I have a 2015 Tahoe LTZ 5.3 4wd. Its done 97k miles now. Since new its been maintained by the dealership. I had some questions:

1. Between 60 and 65mph, there is a very faint whining sound from the back. I believe its the differential. But the noise is very hard for someone new to hear. From the RPO Codes: GU6 (3.42 ratio) and G80 (limited slip). Whats the way around it? Should i get a diff. rebuild kit?

2. I am attaching a sound clip. There is a faint sound (comes up 3 times in the audio). This is from inside the well of the front left (driver side) wheel. Usually comes before parking the truck after a drive.

3. The brakes feel a bit spongy. When i apply full brakes from lets say 40mph, i feel as though the abs engages earlier than it should. no issues otherwise with the braking. I heard the vacuum pumps on these models go bad? No clue if mine is going (there's no clicking sound at idle which i guess is the first sign). I found this video on youtube which gives a diagnostic test. any clue how to do this diagnostic test on my truck and what part #s are relevant for the truck i have?

4. there is a switch to move the pedals. when i press the switch there is some motor-y sound from the pedals but they dont move.

5. on v4 mode and at a very low speed, there is a vibration-y sound somewhere behind the steering wheel. there's no actual vibration in the steering or wheels. just an annoying sound that goes away above and below that resonant speed/rpm.

the truck has been faithful throughout. just some of these issues that i want to get sorted.

 

[2015LTZ]

anyone?

 

[tuckerrnr1]

I'll take a stab at no. 5. It very well could be from the AFM which controls the 4-8 cylinder activation. I had that in my 2010 and the Range plug in to deactivate that solved the vibration.

 

[2015LTZ]

I'll take a stab at no. 5. It very well could be from the AFM which controls the 4-8 cylinder activation. I had that in my 2010 and the Range plug in to deactivate that solved the vibration.

hey thanks a lot. this plug in device, could you send me a link? mine is a 2015 5.3 4wd LTZ

 

[tuckerrnr1]

https://www.rangetechnology.com/products/afm-dfm_disabler/

Punch in your information and when it arrives just insert in the obd port and it does its magic.

 

[2015LTZ]

https://www.rangetechnology.com/products/afm-dfm_disabler/

Punch in your information and when it arrives just insert in the obd port and it does its magic.

thanks a lot!

 

[MikeK1981]

I'm not sure about the diff issue, but I just had my vacuum pump replaced for free by the dealer a couple weeks ago. One day I got little to no brake assistance in a parking lot all of a sudden. We were out of town but I was able to drive it to the closest les schwab. Drove fine on the way there even. They tested it and the pump was going bad, but gm tech support told them over the phone that they are covered under an extended coverage safety recall, up to 150k miles. So I was able to drive it safely home and the dealer here fixed it no charge. It's safe to drive for the most part if the motor is spun up, but if the motor is at low rpm the pump starts to struggle to keep the pressure at a steady level for the brakes, causing you to have to push on the pedal way harder than expected. Obviously a serious safety issue, so i would get fixed now before you drive it much more. If it happened at the wrong moment it could drastically increase your stopping distance at a very bad time. Hit up your dealer and they should take care of it for you!

 

[MikeK1981]

Hello everyone,

A newbie here but I've found a lot of answers to some common problem from this forum.
I have a 2015 Tahoe LTZ 5.3 4wd. Its done 97k miles now. Since new its been maintained by the dealership. I had some questions:

1. Between 60 and 65mph, there is a very faint whining sound from the back. I believe its the differential. But the noise is very hard for someone new to hear. From the RPO Codes: GU6 (3.42 ratio) and G80 (limited slip). Whats the way around it? Should i get a diff. rebuild kit?

2. I am attaching a sound clip. There is a faint sound (comes up 3 times in the audio). This is from inside the well of the front left (driver side) wheel. Usually comes before parking the truck after a drive.

3. The brakes feel a bit spongy. When i apply full brakes from lets say 40mph, i feel as though the abs engages earlier than it should. no issues otherwise with the braking. I heard the vacuum pumps on these models go bad? No clue if mine is going (there's no clicking sound at idle which i guess is the first sign). I found this video on youtube which gives a diagnostic test. any clue how to do this diagnostic test on my truck and what part #s are relevant for the truck i have?

4. there is a switch to move the pedals. when i press the switch there is some motor-y sound from the pedals but they dont move.

5. on v4 mode and at a very low speed, there is a vibration-y sound somewhere behind the steering wheel. there's no actual vibration in the steering or wheels. just an annoying sound that goes away above and below that resonant speed/rpm.

the truck has been faithful throughout. just some of these issues that i want to get sorted.

I didn't hit the reply button before, but see my previous post about your brakes!

 

[testhomer]

I'm not sure about the diff issue, but I just had my vacuum pump replaced for free by the dealer a couple weeks ago. One day I got little to no brake assistance in a parking lot all of a sudden. We were out of town but I was able to drive it to the closest les schwab. Drove fine on the way there even. They tested it and the pump was going bad, but gm tech support told them over the phone that they are covered under an extended coverage safety recall, up to 150k miles. So I was able to drive it safely home and the dealer here fixed it no charge. It's safe to drive for the most part if the motor is spun up, but if the motor is at low rpm the pump starts to struggle to keep the pressure at a steady level for the brakes, causing you to have to push on the pedal way harder than expected. Obviously a serious safety issue, so i would get fixed now before you drive it much more. If it happened at the wrong moment it could drastically increase your stopping distance at a very bad time. Hit up your dealer and they should take care of it for you!

@MikeK1981 - Did your Tahoe have a stored code at all? Or did the dealership just listen to your concerns and do the "proactive" thing and just fix it without making you have a stored code in order for them to do the work?

 

[MikeK1981]

@MikeK1981 - Did your Tahoe have a stored code at all? Or did the dealership just listen to your concerns and do the "proactive" thing and just fix it without making you have a stored code in order for them to do the w

@MikeK1981 - Did your Tahoe have a stored code at all? Or did the dealership just listen to your concerns and do the "proactive" thing and just fix it without making you have a stored code in order for them to do the work?

Les Schwab pressure tested it. And GM tech support is who told Les Schwab about the extended coverage over the phone. Otherwise, Schwab could have done it for me on my own dime if i had wanted. When I called my dealer to ask about it he didn't even question it, so I think they are well aware of the problem. He just set up an appointment for me and that was it. No codes for it that I'm aware of. They just have a problem sometimes maintaining steady pressure when the engine is at low rpm or idle. That's why I was able to drive it 3 hours home safely on the highway. They should be able to pressure test it just like schwab.