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Old 01-06-2009, 09:51 AM   #1
Darkitec
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Default Extreme Down shifting


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I just bought a used 03 Tahoe. with about 68000 miles on it.

While traveling recently I noticed something that seems wrong or at least very strange.

With the cruise control activated above 60MPH and going up hills the transmission would shift from 4th down to 2nd to maintain speed. This seems rather extreme. Kicking off the cruse and putting my foot into the gas it sifted down to third and worked just fine. Does anyone else experience this? What is wrong here? Is there a simple fix to alleviate or minimize this problem?

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Old 01-06-2009, 10:26 AM   #2
667theneighbour
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Is it a steep hill? My 04 only use 2nd if I kick it at lower speeds. Up a 9% hill it uses 3rd to maintain 50-60.
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Old 01-06-2009, 11:29 AM   #3
EliteTahoe
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same problem with my hoe 2000 5.3.
Not any better with supercharger kickin in 2nd gear 4krpm
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Old 01-06-2009, 11:34 AM   #4
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Maybe a re-programming can solve the issue?
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Old 01-06-2009, 12:19 PM   #5
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I think these trucks are set up from the factory to run p265 tall tires. After I installed my p285 mine would downshift into second also, it was terrible when pulling the boat.
With the taller tires the shift points are all jacked up. I used a hyper tech power programmer to recalibrate mine. It helped a ton.
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Old 01-06-2009, 08:03 PM   #6
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Quote:
Originally Posted by oneradride View Post
I think these trucks are set up from the factory to run p265 tall tires. After I installed my p285 mine would downshift into second also, it was terrible when pulling the boat.
With the taller tires the shift points are all jacked up. I used a hyper tech power programmer to recalibrate mine. It helped a ton.
This may be my problem. The truck came with 285-50's. I was towing a light car during the first part of the trip and assumed that was some of the problem. And tow haul mode made the situation worse. On the way back I wasn't towing or hauling any weight but I did have a 20mph head wind for part of the trip and then the hills on I-40 in west Texas and in New Mexico were giving me fits. I gave up on cruise and the problems went a away. I've made the same trip in a 67 Bonneville and a 04 GTO and neither of them needed to down shift to maintain my speed. and while Bonneville a bit more aerodynamic than the brick it does weigh in at 4,300 lbs.

On a side note, I believe the Tahoe is a drive by wire vehicle, Is there a way to adjust the spring rate on the accelerator pedal? After several hours of driving without the cruise my leg was killing me. The accelerator on my 67 Bonneville and the 04 GTO both live throttle acceleration are much easier to operate.

Last edited by Darkitec; 01-06-2009 at 08:26 PM.
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Old 01-06-2009, 08:08 PM   #7
oneradride
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I'd be willing to bet that it is.........
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Old 01-09-2009, 02:29 AM   #8
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Quote:
Originally Posted by oneradride View Post
I'd be willing to bet that it is.........
Any chance you could describe or narrate what changes you made to the program to get the shift points to act correctly?
I.E. I've never gotten a chance to drive the truck with everything like it should be. I've no idea where to start and what I'm changing.
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Old 01-09-2009, 09:29 AM   #9
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Not much to it really… you plug it in under your dash and the hand held controller asks you a series of questions; one of the questions is: What is the height of your tires. After you have answered all the questions (I think there are about 8 or 10 of them, I did this about 4 years ago) it flashes your PCM and you are good to go. If you get one it will have directions.
If you get one from eBay make sure that the previous owner returned their truck to the stock settings because it will only work on ONE TRUCK AT A TIME. It stores your VIN somehow. Anyway, that’s how I got mine. If it does not come with directions you can get them from the hypertech website. You might also try and chat with Jenna, I think the BB Tunes can also do the same thing, possibly more.
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Old 01-09-2009, 11:28 PM   #10
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Thanks for the info. Looks like its a whole lot simpler than I feared.
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