2012 Yukon shudder/vibration around 1000 rpm and other quirks...

[MmmBrisket]

Hey guys,

I just recently purchased a 2012 Yukon SLT with 57k miles. The car seems to be in great shape overall, but I'm definitely new to the world of Yukons/Tahoes...so I'm hoping you all could offer some expert guidance.

I did do some searching in these forums beforehand about my problem and I'll share what I found below.

Main problem: when I drive on city streets and get to around 30 miles or so and start coasting and the RPMs drop to around 1000 or so...I notice this shudder/vibration as soon as I give it a little gas. It completely goes away at about 1100/1200 rpm.

I kept trying to pinpoint if it was more connected to speed or RPMs and I realized that it was mostly about the RPMs. Even if I'm going 40 or whatever...once it drops down to 1000RPM and I give it a bit of gas, there goes the vibration.

It's not a really strong shudder/vibration, but it's noticeable and annoying. It drives so smooth beyond that quirk and I'd like to get it addressed.

From the posts I've seen, a few have called out:
- Driveshaft alignment
- Torque converter
- U-joint

I'm curious what you all think.

Beyond that main issue, I noticed a few more small quirks:
1) a very slight whining when I turn. Is it normal to whine a bit or could that be a power steering issue surfacing?
2) vehicle start is a little slow in the beginning, almost like the battery is going. It turns over a little slow and then starts right up. I am guessing if I get the battery checked, they'll be able to check the alternator too? Been a while since I've had an issue like this.
3) the vehicle has remote start and it doesn't seem to work if the car has been sitting a bit. but if I click the lock button then hit remote start, it works. I wonder if that's somehow connected to the battery/start issue.

Thanks in advance for any help you can offer!

 

[CaptainAmerica1]

It’s your afm. I. Your dic there’s an option for mode. While driving that mode switches from 4v to 8v or some vernacular close to that. See if the mode changes when you feel the shudder…report back with your findings

 

[gooffeyguy]

I agree, the shudder is from the Active Fuel Management.

As for the remote start, that's how it works. You gotta hit lock then hold the start button a couple seconds.

Sent from my SM-G930V using Tapatalk

 

[MmmBrisket]

It’s your afm. I. Your dic there’s an option for mode. While driving that mode switches from 4v to 8v or some vernacular close to that. See if the mode changes when you feel the shudder…report back with your findings

Cap, are you saying there is a driving mode that will turn off AFM? When I searched AFM for my year online, it seems like articles recommended "delete" or "disable" and both involved some additional parts.

But I'll take a look to see if I have any driving modes.

Thanks for the help, guys!

 

[avalonandl]

No you cannot shut off AFM. You can install a Range device (google it) that overides the AFM and does not let it kick in. You lose about 0.5 to 1 mpg but it prevents it from activating. I use the Range because I have much higher mileage - about 159k miles.

 

[MmmBrisket]

No you cannot shut off AFM. You can install a Range device (google it) that overides the AFM and does not let it kick in. You lose about 0.5 to 1 mpg but it prevents it from activating. I use the Range because I have much higher mileage - about 159k miles.

Ah, got it. Yea, I saw that device in an article I pulled up last night. I'll look into doing that. Thanks!

 

[Foggy]

You can kinda keep the AFM from kicking in: put the gear selector in manual mode,
then put it in 4th gear.. It will shift normally from 1-4 gears... And the afm should
not kick on.. Try that to help pinpoint your issue.
The power steering fluid should be changed.. You can suck out the resevoir
and refill maybe 2-3 times within a week or 2... That should get some of the
contaminants out.
Also, you are now 9 years old.. At that low of mileage, I highly doubt the serpentine
belts have been changed.
You'll need to go thru and change ALL of your fluids and filters. Also spark plugs and
wires. S\
Things go bad/wear over time just as much as mileage. Get that trans serviced
the CORRECT way by dropping the pan and changing the filter.
Front and Rear Differential Fluids. Transfer Case Fluid.
COOLANT... get that old coolant out and replace with new fresh DexCool
You coolant touches everything: don't dismiss it's importance.
And obviously Oil & Filter: use full synth 5w30, and a high quality oil filter
such as wix/acdelco. The number 1 cause for AFM lifter failure is OIL maint.
Oil life monitor is Wrong IMO, change at 50% -- that will be about 3,000 miles or
3-4 months

 

[gooffeyguy]

You can kinda keep the AFM from kicking in: put the gear selector in manual mode,
then put it in 4th gear.. It will shift normally from 1-4 gears... And the afm should
not kick on.. Try that to help pinpoint your issue.
The power steering fluid should be changed.. You can suck out the resevoir
and refill maybe 2-3 times within a week or 2... That should get some of the
contaminants out.
Also, you are now 9 years old.. At that low of mileage, I highly doubt the serpentine
belts have been changed.
You'll need to go thru and change ALL of your fluids and filters. Also spark plugs and
wires. S\
Things go bad/wear over time just as much as mileage. Get that trans serviced
the CORRECT way by dropping the pan and changing the filter.
Front and Rear Differential Fluids. Transfer Case Fluid.
COOLANT... get that old coolant out and replace with new fresh DexCool
You coolant touches everything: don't dismiss it's importance.
And obviously Oil & Filter: use full synth 5w30, and a high quality oil filter
such as wix/acdelco. The number 1 cause for AFM lifter failure is OIL maint.
Oil life monitor is Wrong IMO, change at 50% -- that will be about 3,000 miles or
3-4 months

What if you put manual mode into 5th or 6th, will AFM still activate in those two overdrive gears?

Sent from my SM-G930V using Tapatalk

 

[Foggy]

What if you put manual mode into 5th or 6th, will AFM still activate in those two overdrive gears?

Sent from my SM-G930V using Tapatalk

From what I understand, Yes... in 5th or 6th AFM will kick in even in manual mode

 

[MmmBrisket]

Super helpful list/guidance! Thanks, Foggy!