Tranny issue, need some help figuring it out

[992dr]

Its for an 07 Tahoe PPV
Here's my problem.
When accelerating it drives fine and shifts fine.
It's when I'm at cruising speeds, doesn't matter how fast or slow. If I stay at any speed for even the shortest period of time, it starts to shudder/shake. I feel it in the pedal and the steering wheel.

What are your thoughts on this?

Any info would be appreciated
Thanks

 

[08grey]

I had this issue years ago in a different vehicle at 1500 rpm it would shake. Turned out I had the wrong type of tranny fluid. Changed it out and all was well. Damn jiffy lubes

 

[992dr]

I need to make a date for the tranny to get flushed.
Though I did check it out and its still red.

 

[992dr]

Well, made an appointment for a diagnostics check, nothing came up using HPTuners.
Though I did not know it should have been hooked up while driving and he did not mention it either. It was shuddering at roughly 43mph and up. I took it out with the mechanic to point out the problem, he noticed it later in the drive. One thing he did notice was the converter was not locking up at highway speeds. He hit the brakes while driving and nothing happened, the rpms stayed where they were. I bought a new converter a bigger cooler and a shift kit hoping this would eliminate the issue. Boy was I wrong. Not only is the shudder more pronounced at highway speeds (or in 4th gear) it shudders down low now to around 20/35mph. I'm all for preventative maintenance but I think I just wasted a lot of money, when I should have just bought a new tranny.

Now I have a question. People have mentioned something about V4 and V8 mode and seeing it on the dash. This seems to be one of the culprits to the shuddering/vibration. What is this and where is it located?
Is this an option in the PPV Tahoes?

Thanks

 

[08grey]

The mode you refer to is Afm. It kicks the down to 4 cylinders when you are cruising at highway speed to help mpg. It's supposed to show on the DIY when it kicks in. Not sure if the Ppv have this.

I have a question. When you are cruising if you go to speed up does it shudder the ought the acceleration as well or go away?

You mentioned 4th gear. Can you lock her in a lower gear and get to the same speed and see if it still happens? This will tell if it's really 4th related.


Sounds like you brought good stuff. Don't fret you could have brought a new tranny and found out its a motor mount.

 

[992dr]

Sorry, new to the NNBS scene. What is a DIY? Or, what does it stand for?

Under acceleration it doesn't happen, only when cruising at the same speed. If I'm on the highway or side roads I cant cruise without it happening, as soon as I speed up it goes away.

I will try that tomorrow. I'll hold it in third and see what happens. It just started doing it at lower speeds after getting the work done.

G-d, I hope its not something like a motor mount. It doesn't feel like it but, you never know. I'm going to check all of the mounts tomorrow morning.

Thanks for the reply, I appreciate it.

 

[08grey]

By DIY I meant the screen on the dash. I think it's called that. I have a 6.2 so I don't have Afm. Maybe somebody can chime in and tell if it shows on the cluster when it's in 4 mode or even if it's available on a Ppv

 

[992dr]

I'm not 100% sure but, as far as I know, its available.
I don't have a screen, just a cluster, hah. I have never noticed anything about afm on the dash.

 

[STORMIN08]

When you scroll through the vehicles info scree....
It appears on the instant MPG read out....
V4. Or. V8 .

 

[YukonButICanToo]

I know exactly what you're talking about...it's caused by a transmission lock solenoid (or something like that?), check with the dealer for the replacement http://gmpartsonline.net

I had to replace mine on my Silverado and it went back to normal...my gas mileage also got much better, oddly enough.