Originally Posted by Disgruntled
I have a 2007 Outlook also. The transmission is constantly shifting up and down. It shifts at the slightest incline and sometimes will shift back and forth three times before you get to the top of a hill. I too have taken it back to the dealer twice. They first said it was normal. The second time they installed the latest software on the computer. Nothing has changed. I feel that I am stuck with a lemon which cannot be fixed. I think that in trying to get fuel economy, they made a transmission with too many gears (6) and it continually shifts back and forth. Outside of a total redesign, there is probably nothing that can be done for it. I wish I had kept my Highlander. Also, the cruise control is absolutely worthless because it will shift at the first hint of a slight incline. It will usually shift from 6 to 4 and immediately up to 5. Then, maybe back to 6 and back to 4 and 5 again. It will drive you nuts. I hate it.
Those of you dissapointed with the transmission performance, especially if you own an '07, need to get the May 8th transmission flash upgrade. Many Acadia and Enclave owners who weren't happy with tranny performance have said it is a marked improvement. One of the GM powertrain engineers worked with many forum members to come up with the re-calibrated algorithms. The details are posted below.
ALSO, when in cruise the tranny DOES NOT downshift from 6th to 4th and immediately back to 5th. What it actually does is downshift to 5th WITHOUT torque converter lockup. The next immediate upshift you feel is the torque converter locking back in. All transmissions have to kick out the torque converter to downshift. The May 8th upgrade also includes an April upgrade to help the tranny "hold" higher gear when on an incline without upshifting back to 6th until the hill/grade has leveled back out. Good Luck!
#08-07-30-022: Hesitation or Flat Spot Between 56-80 km/h (35-50 mph) (Reprogram Transmission Control Module) - (May 8, 200
Subject: Hesitation or Flat Spot Between 56-80 km/h (35-50 mph) (Reprogram Transmission Control Module)
Models: 2008 Buick Enclave
2007-2008 GMC Acadia
2007-2008 Saturn OUTLOOK
with FWD or AWD
Some customers may comment on a flat spot or hesitation between 56-80 km/h (35-50 mph) speed range.
The existing transmission calibration is programmed to maximize fuel economy and requires a greater throttle input than some customers would prefer to provide acceleration in this speed range.
A new calibration is available. This new calibration increases the speed required to obtain upshifts and removes TCC apply from 2nd to 3rd gear, thereby reducing engine lugging and improving vehicle response to accelerator input.
Important: This calibration will have a negative impact on fuel economy of 0-1.2 L/100 km (0-2 mpg) combined driving.
To obtain this calibration, contact Techline (TCSC) at 1-800-828-6860 (English) or 1-800-503-3222 (French). Techline will reconfigure the vehicle to make this calibration the default calibration for this vehicle.
The table below shows the Shift Pattern Change at Light Throttle.
Current Calibration New Calibration
Shift MPH KPH MPH KPH
1-2 8 13 12 19
2-3 18 29 20 33
3-4 24 40 31 50
4-5 32 53 43 69
5-6 44 71 56 90
TCC Applied 2nd, 3rd, 4th, 5th, 6th 4th, 5th, 6th
For vehicles repaired under warranty, use:
Labor Operation Description Labor Time
K5364 Transmission Control Module Reprogram with SPS Use Published Labor Operation Time