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Discussion Starter · #1 ·
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I use the Cruise control most of the time when I'm on the highway and I've noticed a slightly annoying characteristic that may be lowering the highway mileage.

I'll be driving anywhere between 60 and 70 with Cruise ON. If I'm going up a hill and the transmission downshifts to maintain speed, it WILL NOT upshift again until I am over the crest of the hill. It doesn't matter how slight the incline becomes, it simply won't shift unless I cancel the cruise control...at which time it will shift to 6th.

When it does this, the engine RPM stays around 2400 for the length of every incline where there is a downshift...which lowers the mileage for a trip. What's puzzling me is that it did not do this when I first started driving it as I remember it shifting up to 6th with cruise ON when driving thru the hilly terrain of Vermont in my 1st 500 miles.

Maybe one of the GM guys can chat with other GM guys at lunch one day to help solve this riddle.
Does anyone else see this behavior?
 

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Re: Cruise Control Observation/Question

I noticed the same characteristic in my AWD Outlook. While I consider it unacceptable, I press the coast button once to get it to upshift, then press the acc button to kick it back up to my desired speed.

tyson
 

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Re: Cruise Control Observation/Question

I posted my answer to this on the other thread where you brought it up, but since you started a new thread, I thought I'd post it here too.

That's the way it works. This is by design to reduce shift busyness. More than likely if it did upshift, it would have to downshift again to keep your speed going up the incline. It used to be the other way early on and people would comment that it shifts too much going up an incline in cruise. I think it's just about right now, but I'm sure there is some stretch of road that people can find where it seems like it should shift sooner. This might be, but I think you'll find everywhere else it's pretty good. I also tend to hear this as being more of an issue in an AWD vs. FWD. The update coming may have a change in it to relax the AWD a bit in this area.

I think part of the problem is that people just aren't used to a vehicle that needs to almost always downshift to climb an incline. It seems like I have this conversation at least a couple times a week. Usually people think there's something wrong because their 4 speed vehicle didn't do this or maybe they have a 6 speed V8 truck that doesn't do it. This vehicle isn't either one of those.

You also might tell me that if you drive with your foot, you can make it upshift on the same incline. That might be true, but it's usually because you can't hold your speed or throttle as steady with your foot as the cruise control can. All cruise cares about is keeping the set speed. It doesn't mind what gear or throttle you're at to do it.

I was just out yesterday driving a brand new 2008 on the highway looking for this issue. The FWD I had behaved exactly as I would have expected it to. This is on the list of things I'm looking at. It's a careful balance though. I can fix it for a problem road you might find, but in doing that it might become more busy everywhere else. That's what I don't want to do.
 

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Re: Cruise Control Observation/Question

bobboots said:
When it does this, the engine RPM stays around 2400 for the length of every incline where there is a downshift...which lowers the mileage for a trip. What's puzzling me is that it did not do this when I first started driving it as I remember it shifting up to 6th with cruise ON when driving thru the hilly terrain of Vermont in my 1st 500 miles.
One more comment. As part of the trans update that's coming, I plan on taking a trip out to the East coast to see how the vehicle behaves out there. In general we usually always go out West for most of our development. We're starting to see lots of complaints coming from people out East that drive in this "hilly" terrain. I think it's more rolling hills back to back that aren't that steep or long which is different from the roads we encounter out West.

I drove to Connecticut and back a few weeks ago looking for a specific issue. I thought in general the trans behaved rather well.
 

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Re: Cruise Control Observation/Question

lzwhb2 - excellent feedback, and thanks for providing it. fwiw, i'm on the east coast and where I noticed it most was heading west on I88. I have no problems with the tranny downshifting to maintain speed on an incline - all vehicles I've owned did this in the same general areas the Outlook does it. The issue I have is once it levels out, or even encounters a decline, the tranny still did not upshift. I don't believe we had a strong head wind that day, but I guess that could be used as part of the explanation. I look forward to hearing how your next trip to the east coast with the tranny update is. Will the same update be made available for the Outlooks?
 

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Discussion Starter · #6 ·
Re: Cruise Control Observation/Question

Thanks for your insite about this concern. What's curious..is that when I first got the car on the road, in the first 1000 miles, it would upshift on a hill. If you have a gyro, you could watch for a change in the incline of 10-20%, then upshift.

If you're coming out East, a good road to test this on...is the Mass Turnpike (90) between Exit 2 and tje Worcester, MA area (exit 10). It is about 60 miles long with many long steep hills at a speed limit of 65.
 

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Re: Cruise Control Observation/Question

Mine does this too and I'm in FLORIDA!!! Flat as a, well, you know! I have been on I-75 and it does exactly what you are describing on as small a hill as we have here such as the incline going over another road----not much of a "hill" at all. I noticed this on our first "roadtrip" (hey,3 1/2 months and less than 1500 miles on the car so far).

FWIW
 

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Re: Cruise Control Observation/Question

The Acadia suffers from a severe lack of torque that only a V-8 or a shorter rear (higher numerically) gear would solve. The little V-6 just doesn't have the beans to drag 5000 lbs. around without shifting...a lot. My previous car was an AWD 300C and with all that torque it stayed in overdrive all day...and it probably weighed a 1000 lbs less. On the same roads the Acadia has to drop a gear and sometimes two to maintain the speed you have the cruise set on. If you shut the cruise off and pedal it on the hills you can get rid of some of the constant shifting. I have given up on that and just let it shift. The FWD with the higher speed rear end is probably even worse than the AWD...2.73 compared to 3.16. Grin and bear it...it's doing the best it can.
 

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Re: Cruise Control Observation/Question

Just so I don't drive lzwhb2 I won't go on andon about the tranny.

This is the only thing I hate aout the Acadia. It's like the tranny has OCD or something.

I will try yet again...any idea when the tranny update will be release to us Acadian's? >:D :p
 

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Re: Cruise Control Observation/Question

Nu2GMC said:
The Acadia suffers from a severe lack of torque that only a V-8 or a shorter rear (higher numerically) gear would solve. The little V-6 just doesn't have the beans to drag 5000 lbs. around without shifting...a lot. My previous car was an AWD 300C and with all that torque it stayed in overdrive all day...and it probably weighed a 1000 lbs less. On the same roads the Acadia has to drop a gear and sometimes two to maintain the speed you have the cruise set on. If you shut the cruise off and pedal it on the hills you can get rid of some of the constant shifting. I have given up on that and just let it shift. The FWD with the higher speed rear end is probably even worse than the AWD...2.73 compared to 3.16. Grin and bear it...it's doing the best it can.
Just a little clarification. The FWD and the AWD both have a 3.16 Final Drive Ratio.
 

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Re: Cruise Control Observation/Question

FWIW I used the cruise control on my AWD for the first time yesterday. Mainly on US-31 in Western Michigan. Had it set at 75mph, sometimes 80mph. For the most part the RPMs stayed right around 2000-2200 while cruising. When we would hit a small hill or long incline, the RPMs would jump to 3200 and the car would thrust forward and put me back in the seat a bit. My wife was wondering what was wrong, but I just took it all in as normal. I hadn't had many opportunities in past cars (4-cyl, 4-spds) to use the cruise control, so my expectations of what it 'should' feel like were non-existent.

I don't feel as if my gas mileage was compromised at all. In fact it turned out to be some of the best gas mileage I have experienced to date with my Acadia. I have just over 1450 miles on the car as of today. The trip with the cruise control was roughly 160 miles and only 1/4 tank of gas was consumed. (22 gal tank/4 = 5.5; 160miles / 5.5 = 29 mpg).
 

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Re: Cruise Control Observation/Question

you didn't get 29 mpg in an awd at 75 or 80. the only way to tell would have been to fill the tank and see how much gas you really used.
 

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Re: Cruise Control Observation/Question

imgntht said:
FWIW I used the cruise control on my AWD for the first time yesterday. Mainly on US-31 in Western Michigan. Had it set at 75mph, sometimes 80mph. For the most part the RPMs stayed right around 2000-2200 while cruising. When we would hit a small hill or long incline, the RPMs would jump to 3200 and the car would thrust forward and put me back in the seat a bit. My wife was wondering what was wrong, but I just took it all in as normal.
I don't like the thrusting forward that puts you back in the seat either. It's one thing when you ask for it, but you shouldn't get that while in cruise. That's being addressed with the new update that's coming.
 

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Re: Cruise Control Observation/Question

This weekend I tried my cruise on a real hill and it did act strange too. It climbed fine but as soon as we began to descend it did not shift. The engine went to 4400 rpm and I killed the cruise. I am not sure what happened, my car has 2200 miles so far in my first month.
 

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Re: Cruise Control Observation/Question

Am I missing something? Do not have my Acadia yet so I have not experienced this. Seems to me as long as the car stays at whatever speed I set I would not care what gear it was in or how much it shifts. When I go down a hill in my current car, I manually switch to 2nd so as to brake with the engine, not the brakes. The RPMs of course go way up until the car begins to slow. Sounds from what I have read that one of the features of the Acadia transmission is that it will brake using the gears automatically so that you are not riding the brakes down hills. I would expect the cruise to shift down to slow the car on a downslope, otherwise my cruise speed of 60 goes to 70+ unless I apply the brakes. Maybe this car is just too smart for all of us?
 

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Re: Cruise Control Observation/Question

You could be right. I let the car downshift on its own when coming back from Yosemite down old Priest's grade and it was awesome. I just lightly touched the brakes and it did the rest. I did not have to touch the gear selector. My previous Montana van required lots of shifting and very smelly brakes to complete the hill.
 

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Re: Cruise Control Observation/Question

My complaint with the cruise control is that it is too aggressive in maintaining speed while going up hill. It seems like the speed only has to drop 1-2mph (at 70mph) and the transmission will be downshifting from 6-5 and also releasing the torque converter lock. I suspect this has a significant negative effect on mpg if you are driving in areas with rolling hills. Also, the 6-5 shift is a little obnoxious, so you prefer it to not happen constantly. If I was driving without the cruise, in the same conditions, I would let the speed drop 4-5mph before pushing the throttle hard enough to cause the downshift. I realize this is an area where everyone would have a different opinion, but I have never owned a car that was this aggressive on maintaining speed while going up hill with cruise control. By the way, I really need to use cruise control on this car or I constantly find myself going much faster than what I intend.
 

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Re: Cruise Control Observation/Question

lzwhb2 said:
imgntht said:
FWIW I used the cruise control on my AWD for the first time yesterday. Mainly on US-31 in Western Michigan. Had it set at 75mph, sometimes 80mph. For the most part the RPMs stayed right around 2000-2200 while cruising. When we would hit a small hill or long incline, the RPMs would jump to 3200 and the car would thrust forward and put me back in the seat a bit. My wife was wondering what was wrong, but I just took it all in as normal.
I don't like the thrusting forward that puts you back in the seat either. It's one thing when you ask for it, but you shouldn't get that while in cruise. That's being addressed with the new update that's coming.
lzwhb2

Any better timing of when this update will occur? It seems the way you describe the update it seems like it should be soon.
 

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Discussion Starter · #19 ·
Re: Cruise Control Observation/Question

While I am glad to hear that GM is working on smoothing out the transmission operation, I can also say that aside from the aggressive downshift when going up a hill, this Cruise control is implemented pretty well.

I have an '06 Highlander that will jerk ahead if you press resume when only 3-4 mph below the set speed where the Acadia will not do so if it is able to gain speed at a reasonable rate. My Dodge Grand Caravan had the least aggressive cruise control but still maintained speed within 1-2 mph. In that vehicle, it would allow up to 7-10 seconds to "resume" a previous setpoint without a downshift as long as it was able to accelerate at a reasonable rate during that period.

Perhaps another option would be to allow us to nudge the transmission up a gear when we are on cruise control...if we run in the "L" gearshift position. Right now, that control functions as a limit preventing the transmission from shifting beyond the gear limit set. If we set that to "L" and gear "6", if we bumped the "+" control on the shift lever, it could sighal the tranny to give us an early shift up one gear.

This manual bump-up could be allowed most any time while in "L" with the obvious possible side-effect that you may shift too early and the transmission may have to downshift if it does not have sufficient torque to stay in the higher gear. It could limit how often you are permitted to do this if it is causing too much shifting and would cause excessive heat or excessive wear.
 

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Re: Cruise Control Observation/Question

I agree it does need more torque but we have to live with what we have. Look at the tach at 72 m.p.h. it only turns around 1700 to 1800 r.p.m. that is pretty low for the small engine. I live in kansas and it seems to downshift on any small incline also. It seems to do better when it was colder outside and the a/c was off.
 
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