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#1 Mike2500HD

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Posted 01 January 2009 - 02:05 PM

2007 2500 HD, 6.0, 6 speed auto. heres my questions. First the obvious issue is the trans is programmed to upshift too fast and downshift too slow. I have been tapping it into tow-haul mode to get a downshift when I want it, then taping it out when im ready for an upshift. Is there any info as to wether this can damage the trans? Second, do any of the over the counter chips address this in a really effective way? I dont want hard shifts, I dont want to loose fuel economy. All I want is for the trans to upshift like it should. If im going up hill and the gear I'm in is fine....I dont want it to upshift 2 gears like it does, forcing me to hit the gas so hard it kicks in and downshifts 2 gears until i let off a bit....then upshifts right away again... I mean it upshifts on ahill until im loosing speed, then wont downshift until I floor it. Do any of the custom programmers address this without costing real world drivability? Its obvious GM programmed the trans for max MPG on the test track. In the real world it doesnt work properly. Im sure this is no news to the owners but I'm interested in how people have dealt with it, and if the tow haul mode tap is a problem? Thanks guys...

#2 See Ya

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Posted 01 January 2009 - 03:42 PM

I heard about the newer silverados 6 speed having trouble like this. I think someone posted here about how they used a tuner and it ran better, but I'm not sure where.
Moved on.

#3 BuckFeverZ

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Posted 01 January 2009 - 04:01 PM

Have you talked to the dealer? I know on some of these issues they can reflash your truck but I'm not sure if they can do anything with shift points???

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#4 deepblue HD

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Posted 01 January 2009 - 04:11 PM

I have a 08 2500 hd with the 6.0 and 6 speed. Mine works great around town and hills in the country. I found the problem when towing on the highway in tow haul. It wanted to shift back and forth between 5th and 6th. I just put it in manual and leave it in 4th or 5th. I have a superchip and they have not got a tune for the transmission yet. I contacted them and they said they are working on one and it should be out in the future.
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#5 Mike2500HD

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Posted 01 January 2009 - 04:18 PM

Have you talked to the dealer? I know on some of these issues they can reflash your truck but I'm not sure if they can do anything with shift points???

You know... its not really that horrible. more like an annoyance. But it really must cost me fuel. The trans upshifts just a quikly as it can on light throttle. It works ok most of the time but when you are going up a slight hill it upshifts too soon. To the point that you cant maintain speed. So you give it a bit more throttle...nothing...bit more...nothing...still loosing speed..then you give it more and it down shifts 2 gears and accelerates. but if you back off enough to just maintain speed...it immediately upshifts again until you are loosing speed again. So I've been hitting the tow haul mode to hold gears a bit longer. It works, even though its a pain if im drinking coffie on the way to work, but I worry it might screw up the tranny some how. I had a 95 Yukon with the E4od trans and it did the same sort of thing but with only 4 gears it was really a pain. I know its all about fuel economy ratings. Its big brother you know?

#6 Mike2500HD

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Posted 01 January 2009 - 04:21 PM

Have you talked to the dealer? I know on some of these issues they can reflash your truck but I'm not sure if they can do anything with shift points???

No I didnt talk to the dealer. I dont have much faith in the dealerships. But I did talk to them about altering the TPS monitor pressures so I could run reasonable pressure without always having the stupid light on...They said they could but wanted me to pay for the hours of labor...and I just feel like thats bullshit.

#7 sonjaab

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Posted 02 January 2009 - 01:06 PM

Ahhhh.............The complaints on the new "wondertranny" continue!!!!!
People carried on and on about GM and others not bringing the 6 speed
to market sooner and now that they have it.....................

Anyhoo................Mine shifts like crazy and after almost 2 years I am
used to it by now and it works fine. As far as altering the shift points I am
sure your outta luck as I haven't heard of any reflash update from GM or
even the aftermarket tuner guys.............................

As far as your TPMS your lucky ANY dealer will modify the settings for
you! Most won't even for the hour of Tech-2 playtime that most are
willing to pay for.

If your still under the 3/36k? new car warranty try this:
If you want it done for free.......Just run one of your tires 10 lbs. under
the factory pressure for a few run cycles till the warning message cannot
be reset thru your DIC controls. Take to dealer and have them reset the
TPMS with the Tech-2 and ask/beg/yada for them to modify the pressure
values so you can run a lower pressure.

I did this for them to adjust my stock LT 245-16 pressures from 50 frt./80r
to 45 psi all the way around so I could run a lower pressure while not
towing or hauling for a softer ride............................

#8 VMax2007

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Posted 02 January 2009 - 01:13 PM

Anyhoo................Mine shifts like crazy and after almost 2 years I am
used to it by now and it works fine. As far as altering the shift points I am
sure your outta luck as I haven't heard of any reflash update from GM or
even the aftermarket tuner guys.............................


Wrong, Justin (Black Bear Performance) can and will tune your 6 spd. But since the TCM is internal, it would need to be a live tune. But soon, when the EFI Live Autocal is released, it can be tuned remotely.

Also, my local dealer changed my nominal TPMS setting for me no problem. It did cost me $65 though.

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#9 txdutt

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Posted 02 January 2009 - 09:18 PM

there is an alternate engine/tranny calibration the dealer can install--it's on a TSB that came out summer 2007. I had it installed on mine in March & it made a world of difference in the way the truck drove...got even better when I put in the Bullydog tune in August!!

Edited by txdutt, 02 January 2009 - 09:19 PM.

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#10 pm26

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Posted 02 January 2009 - 10:18 PM

That's where the beauty of a manual 6 speed comes in. You, the driver decide when to shift, not some half ass computer program. Unfortunately, no more manual transmission for these trucks, as people are too lazy to ask for them.

I wish they would have several selectable shifting modes for these auto transmissions. For example, economy mode, and performance mode.

#11 deepblue HD

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Posted 02 January 2009 - 10:26 PM

That's where the beauty of a manual 6 speed comes in. You, the driver decide when to shift, not some half ass computer program. Unfortunately, no more manual transmission for these trucks, as people are too lazy to ask for them.

I wish they would have several selectable shifting modes for these auto transmissions. For example, economy mode, and performance mode.


I went out and tried to get it to do what he is talking about, and it worked great. tow haul is like a performance mode and it wont hurt the trans to keep it in Tow haul
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#12 irengineer

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Posted 03 January 2009 - 02:17 AM

2007 2500 HD, 6.0, 6 speed auto. heres my questions. First the obvious issue is the trans is programmed to upshift too fast and downshift too slow. I have been tapping it into tow-haul mode to get a downshift when I want it, then taping it out when im ready for an upshift. Is there any info as to wether this can damage the trans? Second, do any of the over the counter chips address this in a really effective way? I dont want hard shifts, I dont want to loose fuel economy. All I want is for the trans to upshift like it should. If im going up hill and the gear I'm in is fine....I dont want it to upshift 2 gears like it does, forcing me to hit the gas so hard it kicks in and downshifts 2 gears until i let off a bit....then upshifts right away again... I mean it upshifts on ahill until im loosing speed, then wont downshift until I floor it. Do any of the custom programmers address this without costing real world drivability? Its obvious GM programmed the trans for max MPG on the test track. In the real world it doesnt work properly. Im sure this is no news to the owners but I'm interested in how people have dealt with it, and if the tow haul mode tap is a problem? Thanks guys...


Mike,

The first two items that you mention are upshifting too fast and downshifting too slow.

As you've noticed, it seems the 2007-8's were designed to upshift at low vehicle speeds when at low accelerator pedal positions, in order to keep engine rpm low and thereby maximize fuel economy. Others have previously mentioned that they find these speeds to have been to low for some driving conditions. As for the downshifting, there is a speed range in the 2007-8's between about 37-50 mph (for a 3.73 axle ....speeds would be lower for a 4.10 axle) where when you get a downshift from 6th gear it is automatically a downshift into 4th gear. This might give you more performance than you were looking for.
's
You can imagine that since in that speed range (37-50 mph) you have 5 gears available (6th, 5th, 4th, 3rd, and 2nd) it's a balancing act trying to decide where to put the downshift points. So there are downshifts into 4 different gears that must be positioned between 0 and 100% pedal (but really it's more like between 35 and 100% pedal since there has to be some pedal travel before the first downshift is commanded. To further complicate matters if more than one downshift point is crossed as the pedal is depressed then the shifts could be commanded in one step or in multiple steps depending on how quickly the second shift point was crossed after the first one was commanded. When the shifts are done in multiple steps there are two distinct acceleration changes and the second one is bound to feel a little bit delayed. It's likely that trying to avoid this multiple step downshift condition led to automatically commanding a double step downshift. I think some of the other 6 speed trucks did this in 2007-8 as well (Escalade, Denali?)

In a recent post, txdutt mentioned that there was an an alternate engine/transmission calibration available. I did a search and found it. Take a look at TSB#07-06-04-034. That TSB covers a number of items due to low power compaints. For example, the engine calibration improves performance under hot ambient air conditions, and the transmission calibration revises shift points. You WILL notice a difference in the shift points. Where before you were in 6th gear by about 42 mph (3.73 axle) at low pedal positions, the new calibration moves that point to about 53 mph. Similar for 5th gear (33 mph moves to 42 mph) and 4th gear (24 mph moves to 28 mph). These changes could help address your comment about upshifting too early.

Another thing the alternate transmission calibration does is separate the downshifts mentioned above so that the automatic 6-4 is eliminated. Due to 6th gear not being available until higher speeds the 6-4 isn't an issue in that speed region.

There are two things to consider up front before getting the new calibration(s) - (The TSB recommends that you get both the engine and trans calibrations if you get the update, but technically you could do just one or the other - I'd recommend both). The first thing is that your fuel economy may change. Some people have boasted about fuel economy numbers approaching 16 mpg but the change in shift points is going to result in higher engine speeds at some vehicle speeds and therefore will likely burn more fuel and reduce mpg. However for those who spend most of their time above 53 mph you might not see much of a difference since 6th gear is 6th gear. Also since presumably you'll be in a better gear more often you'll have fewer downshifts to a high engine rpm and have better FE as a result. The second thing to keep in mind is that with higher speed light throttle upshift points comes higher speed coastdown points. You may notice a bit of a bump as you slow down and change gears from 6-5, 5-4 and 4-3.

Conclusion. Based on your comments I'd suggest you get the alternate cal. I think your fuel economy difference will be minimal and the coastdown bump will be tolerable as well.

IRE

Attached File  TSB_07_06_04_034___Low_Power___Engine_Trans.pdf   105.36KB   83 downloads
2007 Sierra 2500 HD K25743 Black
2009 Yukon XL 2500 HD K25906 Black
2009 Silverado 2500 HD K25943 Red
2009 Sierra 2500 HD K25743 Gray
2010 Sierra 2500 HD K25743 Black
2010 Yukon XL 2500 HD K25906 Black
2011 Sierra 2500 HD K25743 Black
2011 Sierra 2500 HD K25743 Black

#13 Mike2500HD

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Posted 05 January 2009 - 11:00 PM

2007 2500 HD, 6.0, 6 speed auto. heres my questions. First the obvious issue is the trans is programmed to upshift too fast and downshift too slow. I have been tapping it into tow-haul mode to get a downshift when I want it, then taping it out when im ready for an upshift. Is there any info as to wether this can damage the trans? Second, do any of the over the counter chips address this in a really effective way? I dont want hard shifts, I dont want to loose fuel economy. All I want is for the trans to upshift like it should. If im going up hill and the gear I'm in is fine....I dont want it to upshift 2 gears like it does, forcing me to hit the gas so hard it kicks in and downshifts 2 gears until i let off a bit....then upshifts right away again... I mean it upshifts on ahill until im loosing speed, then wont downshift until I floor it. Do any of the custom programmers address this without costing real world drivability? Its obvious GM programmed the trans for max MPG on the test track. In the real world it doesnt work properly. Im sure this is no news to the owners but I'm interested in how people have dealt with it, and if the tow haul mode tap is a problem? Thanks guys...


Mike,

The first two items that you mention are upshifting too fast and downshifting too slow.

As you've noticed, it seems the 2007-8's were designed to upshift at low vehicle speeds when at low accelerator pedal positions, in order to keep engine rpm low and thereby maximize fuel economy. Others have previously mentioned that they find these speeds to have been to low for some driving conditions. As for the downshifting, there is a speed range in the 2007-8's between about 37-50 mph (for a 3.73 axle ....speeds would be lower for a 4.10 axle) where when you get a downshift from 6th gear it is automatically a downshift into 4th gear. This might give you more performance than you were looking for.
's
You can imagine that since in that speed range (37-50 mph) you have 5 gears available (6th, 5th, 4th, 3rd, and 2nd) it's a balancing act trying to decide where to put the downshift points. So there are downshifts into 4 different gears that must be positioned between 0 and 100% pedal (but really it's more like between 35 and 100% pedal since there has to be some pedal travel before the first downshift is commanded. To further complicate matters if more than one downshift point is crossed as the pedal is depressed then the shifts could be commanded in one step or in multiple steps depending on how quickly the second shift point was crossed after the first one was commanded. When the shifts are done in multiple steps there are two distinct acceleration changes and the second one is bound to feel a little bit delayed. It's likely that trying to avoid this multiple step downshift condition led to automatically commanding a double step downshift. I think some of the other 6 speed trucks did this in 2007-8 as well (Escalade, Denali?)

In a recent post, txdutt mentioned that there was an an alternate engine/transmission calibration available. I did a search and found it. Take a look at TSB#07-06-04-034. That TSB covers a number of items due to low power compaints. For example, the engine calibration improves performance under hot ambient air conditions, and the transmission calibration revises shift points. You WILL notice a difference in the shift points. Where before you were in 6th gear by about 42 mph (3.73 axle) at low pedal positions, the new calibration moves that point to about 53 mph. Similar for 5th gear (33 mph moves to 42 mph) and 4th gear (24 mph moves to 28 mph). These changes could help address your comment about upshifting too early.

Another thing the alternate transmission calibration does is separate the downshifts mentioned above so that the automatic 6-4 is eliminated. Due to 6th gear not being available until higher speeds the 6-4 isn't an issue in that speed region.

There are two things to consider up front before getting the new calibration(s) - (The TSB recommends that you get both the engine and trans calibrations if you get the update, but technically you could do just one or the other - I'd recommend both). The first thing is that your fuel economy may change. Some people have boasted about fuel economy numbers approaching 16 mpg but the change in shift points is going to result in higher engine speeds at some vehicle speeds and therefore will likely burn more fuel and reduce mpg. However for those who spend most of their time above 53 mph you might not see much of a difference since 6th gear is 6th gear. Also since presumably you'll be in a better gear more often you'll have fewer downshifts to a high engine rpm and have better FE as a result. The second thing to keep in mind is that with higher speed light throttle upshift points comes higher speed coastdown points. You may notice a bit of a bump as you slow down and change gears from 6-5, 5-4 and 4-3.

Conclusion. Based on your comments I'd suggest you get the alternate cal. I think your fuel economy difference will be minimal and the coastdown bump will be tolerable as well.

IRE

Attached File  TSB_07_06_04_034___Low_Power___Engine_Trans.pdf   105.36KB   83 downloads

Thanks IRE, what you describe is pretty much what I have been observing, put into more technical terms. I also understand the logic and all from GM's perspective. Its just a minor finesse kind of thing. And yes I really dislike the 6 to 4 downshift. Most of the time when it does that 5th would be perfect under that sercomstance. Im not so much worried about performance from the exceleration side. As if I step into it she goes like hell. Sounds like a hot rod.. etc. However its that normal driving commuting mode where I just want a lazy one gear downshift to maintain on an upgrade... and it wont do it. It insists on dropping 2 gears and costing me fuel. or upshifting until its lugging and loosing speed forcing me to apply too much throttle just to either keep it from upshifting... or if I was too slow, to force a downshift. And there was one of my questions. Wether or not it was advisable to keep tapping into tow-haul to ease a downshift. The tapping out to go back to normal. Thanks. M.R.

#14 SS Crew

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Posted 05 January 2009 - 11:56 PM

Have you talked to the dealer? I know on some of these issues they can reflash your truck but I'm not sure if they can do anything with shift points???


Do not get the updated shift reprogram!!!
It shifts worse, won't shift into 5th until a 50+mph, then when you slow down you can feel the trans downshift into 2nd.

Once you have the new program installed GM won't let the dealers downgrade to the original program - you can only go up.

Be careful what you ask for.....
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#15 98silvz71

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Posted 06 January 2009 - 09:04 AM

Have you talked to the dealer? I know on some of these issues they can reflash your truck but I'm not sure if they can do anything with shift points???


Do not get the updated shift reprogram!!!
It shifts worse, won't shift into 5th until a 50+mph, then when you slow down you can feel the trans downshift into 2nd.

Once you have the new program installed GM won't let the dealers downgrade to the original program - you can only go up.

Be careful what you ask for.....


You mean it shifts like an Allison without paying for the Allison? Awesome. I would totally get it done if I had the 6-speed gas engine. :dunno:

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