GMC Acadia Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
I have a 2007 SLT. We recently went on a trip and the check engine light came on. My husband was driving and after the light came on, we were having problems taking off after a traffic light. He would press the accelerator and the engine would rev up like it was in neutral and the car would not move very fast. The car is still under the 3 year 30,000 mile warranty (barely with 25,000 miles) so I took it in today to a GMC dealer. The dealer said that there was a problem with an old code in the transmission which caused the light to come on. Would this code also cause the problem with the acceleration? A couple of other things we are experiencing is a rattle (in the morning) when you accelerate and the car seems noisier at higher speeds. We've already had the steering rack and steering pump replaced so I don't think it's those. Any suggestions? The garage couldn't find anything wrong with it all.
 

·
Premium Member
Joined
·
3,374 Posts
Welcome to the forum.

Codes are set by the computer in the vehicle when a malfunction is detected by one of the sensors. I think the dealer was referring to a reprogramming of the transmission, known here as the "May 8 flash" since it was an update for the transmission software that was released on May 8, 2008. The dealer would be able to check the service history for the vehicle in the GM computer and tell if this had ever been done.

If the engine light is on, depending on the code, the engine can enter a "limp home" mode where power is reduced.

The rattle you described is too generic to try & troubleshoot. You'll have to narrow down what part of the vehicle it is originating from- sometimes it takes two people, one to drive and one inside or outside to listen for it.

One issue that did come to light recently were the driveshaft bolts in the AWD mechanism on the 2007 models. This may or may not apply to your vehicle.

If you will be so kind as to update your profile with your location and your signature with your vehicle year, model, FWD/AWD, and options, it will make it easier for you to receive answers here.

The instructions for doing so are in the Blues Clues link in my signature.
 

·
Registered
Joined
·
10 Posts
Ours was doing something similar. It happened to my wife on here way home from work (engine rev'd up but wouldnt go faster than about 20-30 MPH, check engione light went on). When I took it for a test ride after she got home it was pretty much fine. Took it to the dealer the next day, the check engine light went out ..of course. They replaced the speed sensor. A week or two later it happened again on her way to work. I stopped over at lunch to take it to the dealer. It would not go into reverse, and wouldn't go forward faster the 20-25 MPH. It would stay in 1st or 2nd gear. It is currently at the dealer... they are replacing the transmission (I think... although I haven't talk to them since taking it in). Good think you have it documented with the dealer, so they should cover any issues further down the road, should it act up again like ours has. Good luck...
 

·
Premium Member
Joined
·
14,870 Posts
zogy said:
Ours was doing something similar. It happened to my wife on here way home from work (engine rev'd up but wouldnt go faster than about 20-30 MPH, check engione light went on). When I took it for a test ride after she got home it was pretty much fine. Took it to the dealer the next day, the check engine light went out ..of course. They replaced the speed sensor. A week or two later it happened again on her way to work. I stopped over at lunch to take it to the dealer. It would not go into reverse, and wouldn't go forward faster the 20-25 MPH. It would stay in 1st or 2nd gear. It is currently at the dealer... they are replacing the transmission (I think... although I haven't talk to them since taking it in)[/color]. Good think you have it documented with the dealer, so they should cover any issues further down the road, should it act up again like ours has. Good luck...
What kind of miles does the vehicle have.....city or highway? You may be a first in getting a new trans (at least for the members that are here).
 

·
Registered
Joined
·
10 Posts
Turns out they did not end up replacing the transmission. They disassembled it and repaired it. The problem was a failure of an internal part on the 3-5-Reverse clutch assembly...I believe they said it was a snap ring, or a wave-plate failure. Everything is working fine after the repair. I found a few (3 or 4) other occurances of similar symptoms (no reverse, engine revs but speed is limited to 20-25 MPH), so it appears to be a somewhat uncommon.... although no isolated. failure. On a side note: the engine reving, and lack of speed appears to be the transmission going into a "limp-home" mode, so there could be other problems that would cause this same symptom. Here is a post I put on the Forum describing the situation and the resolution:

"This was a recent problem that I have seen 3 or 4 other posts about so I thought I would document my findings for others on the forum. The first sign of a problem was the engine would rev and the vehicle speed would be limited to 20-30 MPH’ basically, I believe the transmission was in a limp-home mode. The first time it happened, the symptoms went away and the car drove normally; although the Check Engine light was illuminated. We took it to the dealer, and they replaced the Input Speed Sensor. After the car was returned from the dealer I noticed that it would take a few seconds (~2-3) before it would engage into Reverse, and the 2 to 3 shift was a bit more noticeable than normal. After about a week, the problem returned (engine reved, but would not go faster than 30 MPH)… but this time there was NO Reverse gear at all. I drove it to the dealer, which was thankfully only a few miles away, and after disassembling the transmission replace the 3-5-Reverse wave plate, clutch pack and few other related items. Apparently the snap ring, or other components in the 3-5-Reverse clutch pack failed. It’s been a week since the repair and all seems to be back to normal. An interesting side note is that it would not start on the first attempt after cycling through the gears (e.g. after you take if out of Drive and put it into Park, and turn off the key… it would not start on the first try). This turned out to be a bad connection in the 20-pin connector goes between the transmission and the ECU (see my other post “wont start, will not start..”). I hope this helps others out there, that may be suffering similar symptoms …. Looks like some trans work ahead. Oh yeah, my Acadia is a 2007, with ~ 40,000 miles, and all this was covered under Warranty. …. Now I can get the May 2008 transmission reflash done… "
 

·
Premium Member
Joined
·
14,870 Posts
Glad to hear you got resolution; your dealership must be one of the one's selected to stay on with GM :thumb:
 
1 - 6 of 6 Posts
Top