Going Up to the Mountain with 8V AWD - Page 2

ascariSTS · #16 (**permalink**) 01-23-06, 01:41 AM

Isn't it because STS is 5 speed ???

I mean, nasser said he didn't notice this shifting indecision with the old STS (Seville) which is 4 speed...

Don't think that moving for the first time to 5-speed might cause some errors ? (Gear Ratio distribution)

nasser · #17 (**permalink**) 02-19-06, 03:41 PM

Hi Shane
Any news regarding the shifting problem ?
i have stoped using the D and only using the mauall shifting cause this problem makes driving a real pain in the A...
i hope someone found a solution

tedasaurus · #18 (**permalink**) 02-19-06, 11:03 PM

No new news. I have been away from the STS4 for a month now, and it looks like it is going to be another two weeks. When I finally get back to Dallas I will have it looked at and tell you of a remedy if there is one.

hmorse · #19 (**permalink**) 02-20-06, 10:01 AM

I have a new 2006 STS V8: When going up a steep mountain road with some snow and ice, is it best to leave the TC button "ON" or "OFF"? My dealer thinks it would be better "OFF". Your thoughts? What about going DOWN the mountain, same road conditions.

Thanks.

nasser · #20 (**permalink**) 03-12-06, 02:51 PM

Quote:

Originally Posted by tedasaurus

I have the same problem with my '05 STS4. It is subtle, but after living with it for awhile I am torn whether it is the tranny or something along the lines of a bad throttle position sensor. The reason I say this is that after it shifts it does not want to downshift appropriately/progessively (like almost a dead spot followed by indecision) unitl you mash the gas pedal so far down that it skips two gears and blasts you ahead. I have had Cadillac TPS's go bad and this is not far from that. Granted the new car is drive by wire but it has to get its readings from something.
I will have the car looked at next time it is ready for an oil change. I will post a cure if there is one.

hi
any news ?
after having almost 5000 km now I am able to describe the problem better
It seems that whenever the rpm drops to less than 2000 , the gear shifts to the 5th and when I ask for some more power it will shift up to 4th and immediately to the 3rd making a funky feeling
any one experiencing the same ?

Devil_concours · #21 (**permalink**) 03-12-06, 07:43 PM

i would like to know more about this as well. I've noticed the same issue on the sts4 while driving around the residential at 25mph.
I couldn't really tell whether it was the transmission or the awd system.

Zorb750 · #22 (**permalink**) 03-16-06, 02:43 AM

Your car is drunk!

I have a theory. The transfer case for your all wheel drive system takes a little bit of torque off of the engine to operate. This slight reduction in power (probably 7-8 percent, not more than ten percent) may be enough to cause the transmission to be in a point where its programming wants it to shift up a gear, but because of the AWD this leads to lugging the engine along at too low an RPM to produce enough torque to adequately carry the car, which in turn causes it to downshift, then upshift, to sort of float between gears, and perhaps partially engage the torque converter clutch. This could cause it to feel somewhat ... lethargic.

This would be caused by the AWD and RWD cars both having the same transmission programming (wouldn't surprise me, or perhaps some were done incorrectly), which does not take into account the additional power liability from the transfer case.

I am of course not certain that this is the problem, but it does make sense. I've seen it on the early Jeep Grand Cherokees with electronic automatic transmissions. On the part time 4wd models, it would operate perfecly in 2wd, perfect transmission behavior, but as soon as you put it into 4wd, it would start into gear hunting and feel like the transmission was getting confused, sometimes staying in a high gear on a steep uphill (4th gear up hill at 40 mph

), sometimes repeatedly locking and unlocking the TC clutch, or hunting between two gears. The fix was an updated PCM and transmission controller configuration which made the trans controller aware of the state of the 4wd system (on or off).

Perhaps your transmission programming is really for a two wheel drive car, and doesn't take your all wheel drive (and its additional power requirement) into account.

Devil_concours · #23 (**permalink**) 03-16-06, 08:21 AM

Quote:

Originally Posted by Zorb750

Your car is drunk!

I have a theory. The transfer case for your all wheel drive system takes a little bit of torque off of the engine to operate. This slight reduction in power (probably 7-8 percent, not more than ten percent) may be enough to cause the transmission to be in a point where its programming wants it to shift up a gear, but because of the AWD this leads to lugging the engine along at too low an RPM to produce enough torque to adequately carry the car, which in turn causes it to downshift, then upshift, to sort of float between gears, and perhaps partially engage the torque converter clutch. This could cause it to feel somewhat ... lethargic.

This would be caused by the AWD and RWD cars both having the same transmission programming (wouldn't surprise me, or perhaps some were done incorrectly), which does not take into account the additional power liability from the transfer case.

I am of course not certain that this is the problem, but it does make sense. I've seen it on the early Jeep Grand Cherokees with electronic automatic transmissions. On the part time 4wd models, it would operate perfecly in 2wd, perfect transmission behavior, but as soon as you put it into 4wd, it would start into gear hunting and feel like the transmission was getting confused, sometimes staying in a high gear on a steep uphill (4th gear up hill at 40 mph

), sometimes repeatedly locking and unlocking the TC clutch, or hunting between two gears. The fix was an updated PCM and transmission controller configuration which made the trans controller aware of the state of the 4wd system (on or off).

Perhaps your transmission programming is really for a two wheel drive car, and doesn't take your all wheel drive (and its additional power requirement) into account.

i didn't see any similar posts made for srx v8 awd. iirc, it's the same powertrain as the srx

nasser · #24 (**permalink**) 03-16-06, 02:45 PM

do you think my car has the wrong programing ? if so how can i check which program i have ?

Zorb750 · #25 (**permalink**) 03-16-06, 08:30 PM

Maybe the SRX isn't done this way, or maybe just some cars do this. GM is not perfect.

Zorb750 · #26 (**permalink**) 03-16-06, 08:37 PM

Quote:

Originally Posted by nasser

do you think my car has the wrong programing ? if so how can i check which program i have ?

It would have to be done by a dealer. I am not certain that this is the case, it IS only a theory. It just makes sense to me. Do not forget that the all wheel drive came out after the two wheel drive STS. It may need more fine-tuning. There may be a fix in a year or so. You never know. If I hear anything, I will post it here. I DO try to stay on top of all of this stuff, though perhaps not so much as BMW stuff. (Could practically take apart and reassemble E38 7 series while half asleep)

AllWheelEric · #27 (**permalink**) 03-16-06, 10:43 PM

Sounds like a plausible theory. My STS4 feels this way too. I originally thought it was intentionally over-aggressive upshifting in the name of fuel economy. But it could be an engineering oversight.

Zorb750 · #28 (**permalink**) 03-17-06, 12:24 AM

Maybe a combination of both.

nasser · #29 (**permalink**) 03-18-06, 10:31 AM

i think the torque theory is reasonable , i will check it with the dealer and let you know

nasser · #30 (**permalink**) 03-26-06, 05:21 AM

the only way to overcome this problem till now is to use the manual shifting , when driving at low speed keep it on 2nd or 3rd , if you have the HUD it is easier
i am travelling for one week , so i drove my car to the dealer to test it and see if he can help , i gave him the hint about the torque programing ( 2W vrs 4W ) and let's hope he will find a solution