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Discussion Starter · #1 ·
Took a trip this weekend. On the way back. I tried to set cruise at 65 and it would stay in 5th gear until I was either going downhill or reduced the cruise so it would change to 6th. It did this at all speeds up to 76. At 77 it would drop to 6th and pretty much stay there except on uphill climb. This just started doing this and I have not had any problems before. I have about 3600 miles. Any others with similiar problems?
 

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No, I have not had that problem or many of the other tranny complaints that others have had. I have an 07 built in May and delivered June,1. I have noticed very few times some lag but it has been good for the most part. I guess it's time for the dealer to take a look. Good luck.
 

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Do you have the towing package and is it possible you where in tow/haul mode accidently?
 

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Discussion Starter · #4 ·
I do not have the towing package. In fact, I even tried going to the selectable gears and would put it in 5th gear at those speeds and then keep the same speed and put it in 6th and there was no change until I let up on the acceleration then it would shift. It work fined the same way at 77 and above. Strange!
 

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dura_cell said:
Took a trip this weekend. On the way back. I tried to set cruise at 65 and it would stay in 5th gear until I was either going downhill or reduced the cruise so it would change to 6th. It did this at all speeds up to 76. At 77 it would drop to 6th and pretty much stay there except on uphill climb. This just started doing this and I have not had any problems before. I have about 3600 miles. Any others with similiar problems?
I have 9600 miles on mine and at 75 mph it will shift down at the slightest incline or even a small headwind. It's done this since day one and I have given up on it ever changing. Don't hold much hope for change even with the transmission flash that is supposed to be coming later this month. But I'm ready to be pleasantly surprised. Too much weight and not enough torque...although I suffer from the same affliction. ;D
 

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Discussion Starter · #6 ·
I had that problem on occasion until the transmission update. Not the last update but the one before that.
 

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I'm just curious how someone knows what gear you're in...there's no display that I know of?
 

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OK, I confess... I needed it for my Supra (only a 5 speed). ;)

What are the RPMs at the mentioned speeds? I don't know offhand about the gear ratios of the Lambda 6 speed, but since the motor does not have the torque of a V8, I suspect it may well dance around a bit at certain road speeds, especially if there is a grade involved.

The T56 manual 6 speed is a double OD, with a 6th ratio of .50:1. Even with semi-steep (3.73~4.10) gearing (the Lambda is much higher than that, 3.16:1, for the unaware, a higher number here means you can accelerate more quickly and will have a higher engine RPM at a given speed), I am only turning say 2.2K RPM at 75 MPH in 6th gear. This is a killer for acceleration. I have a turbocharged Trans Am with this transmission and the 3.73:1 gearing. It makes over 570 foot-pounds of torque at the rear wheels at around 4K RPM. I can make boost because of the load at this lower RPM, but the motor sure doesn't like it (pinging), so it is better to downshift to 5th. I'm sure the Lambda is programmed the same way.
 

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Phazer_II said:
I'm just curious how someone knows what gear you're in...there's no display that I know of?
I guess it is kind of second nature for some. I subconsciously count shift points on automatics & know what my vehicles are turning (RPM) at any given road speed. Granted, this is easier with 4 speeds vs. 6, but I'll get the hang of the Acadia IF my wife will ever let me drive it.

I didn't do so well with her pickup, so it may be a while for the Acadia.
 

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I had that problem too until had trans flash update in October 07. Been just fine sensing when should be shifting into 6th. I'm unsure if going to get the latest May 08 flash update. Leaving well enough alone for now.
 

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Blue_2009_SLT2 said:
What are the RPMs at the mentioned speeds? I don't know offhand about the gear ratios of the Lambda 6 speed, but since the motor does not have the torque of a V8, I suspect it may well dance around a bit at certain road speeds, especially if there is a grade involved.

The T56 manual 6 speed is a double OD, with a 6th ratio of .50:1. Even with semi-steep (3.73~4.10) gearing (the Lambda is much higher than that, 3.16:1, for the unaware, a higher number here means you can accelerate more quickly and will have a higher engine RPM at a given speed), I am only turning say 2.2K RPM at 75 MPH in 6th gear. This is a killer for acceleration. I have a turbocharged Trans Am with this transmission and the 3.73:1 gearing. It makes over 570 foot-pounds of torque at the rear wheels at around 4K RPM. I can make boost because of the load at this lower RPM, but the motor sure doesn't like it (pinging), so it is better to downshift to 5th. I'm sure the Lambda is programmed the same way.
Blue, here's the gear ratios for the Lambda transmission:
Gear ratios:
First 4.484
Second 2.872
Third: 1.842
Fourth: 1.414
Fifth 1
Sixth 0.742
 

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Thanks Geo.

That 6th OD ratio is similar to an old T5. Seems a little odd that there is only one OD for a six speed, but due to the weight of the vehicle & lower torque of the V6 this must have been calculated to max out the economy and emissions. That is a really low first gear.

I found this info on the Classic Conversions website:
GM T-5 Standard V8 GM T-5 Standard V6 GM T-5 Optional
1ST 2.95:1 3.97:1 3.35:1
2ND 1.94:1 2.34:1 1.99:1
3RD 1.34:1 1.46:1 1.33:1
4TH 1.00:1 1.00:1 1.00:1
5TH .73:1 .79:1 .68:1
Max torque 275 lb ft Max torque 225 lb ft Max torque 300 lb

Note the differences for the V8/V6 lower gears.

Here are the T56 ratios (later model >1993)
Borg Warner 6sp T-56 Gear Ratios
1st 2.66:1
2nd 1.78:1
3rd 1.30:1
4th 1.00:1
5th 0.74:1
6th 0.50:1

These are generally rated for 450 lb ft of torque.

Hard to believe we ever got by with three speed manuals and two speed autos (Powerglides) :). I saw an older P/U for sale the other day & commented on the "three on the tree" on the sign. My kid had no idea what this meant, so I explained it to them. For the younger crowd here, it is a column-shifted manual transmission.
 

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Blue_2009_SLT2 said:
Thanks Geo.

That 6th OD ratio is similar to an old T5. Seems a little odd that there is only one OD for a six speed, but due to the weight of the vehicle & lower torque of the V6 this must have been calculated to max out the economy and emissions. That is a really low first gear.

I found this info on the Classic Conversions website:
GM T-5 Standard V8 GM T-5 Standard V6 GM T-5 Optional
1ST 2.95:1 3.97:1 3.35:1
2ND 1.94:1 2.34:1 1.99:1
3RD 1.34:1 1.46:1 1.33:1
4TH 1.00:1 1.00:1 1.00:1
5TH .73:1 .79:1 .68:1
Max torque 275 lb ft Max torque 225 lb ft Max torque 300 lb

Note the differences for the V8/V6 lower gears.

Here are the T56 ratios (later model >1993)
Borg Warner 6sp T-56 Gear Ratios
1st 2.66:1
2nd 1.78:1
3rd 1.30:1
4th 1.00:1
5th 0.74:1
6th 0.50:1

These are generally rated for 450 lb ft of torque.

Hard to believe we ever got by with three speed manuals and two speed autos (Powerglides) :). I saw an older P/U for sale the other day & commented on the "three on the tree" on the sign. My kid had no idea what this meant, so I explained it to them. For the younger crowd here, it is a column-shifted manual transmission.
My dad had an old FORD Fairlane I think it was with a 3 on the tree.
 

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Mine does the same exact thing, when cruising at 60, stays in 5th, until I go down a hill, or press on the gas a little more, and will shift to 6th. I know what gear I am in as to the RPM's at cruising speeds.
 
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