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Tranmission shifting with Cruise Control on

Shu

By Shu
in Ask A GM Technician

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Shu Enthusiast

Shu

Posted
Posted

This may have been covered already and many times at that, but I am new to the forum and hadn't figured out how to do a search just yet.

 

I have a 2005 Silverado 4x4 with the 4.3L and Automatic. I have noticed that if I do not use cruise control, I can climb hills (highway at 70 mph) and the transmission first unlock the converter, then drop one gear from 4th to 3rd and pull strong. However, if cruise control is used, it will unlock the converter, then drop all the way down to 2nd gear, climb and then jump back into 4th with only a slight, short shift into third.

 

I have taken it back to the dealer and they claim this is normal. Is that true? Because I don't understand why I can drive it without it doing this, but as soon as the cruise is in control of maintaining speed, it shift erratic like this.

 

Any tips on what to look at to correct this? It sure sounds like it is hard on the transmission.

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
I have taken it back to the dealer and they claim this is normal.  Is that true? 

 

Dunno. The cruise does not control the throttle in as small increments as you do with your foot when it's trying to regain significant speed, so I'd say yeah, it's probably normal.

 

Just like when I pull out of a tollgate and hit resume. My truck accelerates pretty hard under the control of cruise, whereas I would probably accelerate more gradually if I was doing it myself. Does that make it abnormal behavior of the cruise? I think not.

Shu Enthusiast

Shu

Posted
  • Author
Posted
I have taken it back to the dealer and they claim this is normal.  Is that true? 

 

Dunno. The cruise does not control the throttle in as small increments as you do with your foot when it's trying to regain significant speed, so I'd say yeah, it's probably normal.

 

Just like when I pull out of a tollgate and hit resume. My truck accelerates pretty hard under the control of cruise, whereas I would probably accelerate more gradually if I was doing it myself. Does that make it abnormal behavior of the cruise? I think not.

 

 

 

 

 

I agree the cruise is less sensitive than the foot, but when the truck drops from 70 (set speed) to about 65 before the computer realizes it isn't holding asteady speed, and then drops two gears to make up for it's slow reaction and then slams back into Overdrive when it catches up....that doesn't seem like it should be normal. At first I thought it was just me with the 4.3L in a 4x4 that was having this problem, but I have heard that all the new GM trucks, regarless of powerplant, perform the same way. I still can not believe GM would think this is acceptable. Anyone else out there have the same complaint? Or better yet solution? :D BTW, I purchased the Hypertech PowerProgrammer III and it allows you to custom tune shift points. Can this be used to reprogram the down shifts? Anyone with experience on this?

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted

Yep,As Wingnut said,Its normal,Both my '99 and my '04 do the same thing.

As far as the Hypertech Power ProgrammerIII,I have one on my '04 (I also had one on my '99) and love it,I wouldn't use anything else,You can reprogram the down shifts/shift points but it won't do anything for the harsh down shifts of the cruise.

Shu Enthusiast

Shu

Posted
  • Author
Posted
Yep,As Wingnut said,Its normal,Both my '99 and my '04 do the same thing.

As far as the Hypertech Power ProgrammerIII,I have one on my '04 (I also had one on my '99) and love it,I wouldn't use anything else,You can reprogram the down shifts/shift points but it won't do anything for the harsh down shifts of the cruise.

 

 

 

 

 

Well I figured it out. ALL GM trucks behave like this, and according to GM it is normal, but that doesn't mean that it HAS to be like this. It is very harsh on the transmission and also on gas mileage. Using the Hypertech ProgrammerIII I was able to stop mine from doing this. It now drives much nicer on the highway. On a steep inclide with the cruise on (and Air as well, and even with the 4.3 L), it will unlock the converter, then drop one gear (if needed) and has plenty of power to pull the hills. It appears the gas mileage has gotten better as well, but I am only about half way through the tank full, so I'll know for sure soon. It also maintains a much steadier speed with cruise on. The simple trick is finding the right shift points to program. On mine, and I'll double check this weekend, I think it was 1-2 shift up 3 pmh, 2-3 shift down 5 mph, 3-4 shift up 3 mph. It is so nice to drive now!

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted

Shu,Yes,Please check your shift points and let us know,I couldn't get the Hypertech to stop the harsh downshifts (with the cruise on) but maybe thats because I have the V8. :crackup:

Shu Enthusiast

Shu

Posted
  • Author
Posted
Shu,Yes,Please check your shift points and let us know,I couldn't get the Hypertech to stop the harsh downshifts (with the cruise on) but maybe thats because I have the V8. :seeya:

 

 

 

 

I do have mine set at +3 mph 1-2 shift, -5 mph 2-3 shift and +3 mph on 3-4 shift. It works perfectly and absolutely no more dropping to second gear on the highway:) Just check my mileage, went from an average of about 15 to 16 up to 18 to 19. I am very pleased with this Hypertech PowerProgrammerIII.

  • 3 weeks later...
Shu Enthusiast

Shu

Posted
  • Author
Posted

I just tried 1-2 shift +3, 2-3 shift -4, and 3-4 shift +2 and that works well too. I'll keep playing with it and find the break point to when it wants to drop to second when pulling hills w/ cc on.

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted

I haven't reprogrammed mine yet,but I might before next weekend because I'm going to Bristol,TN for the NASCAR races and I'll be able to try it out on the trip! :driving:

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted
I am very pleased with this Hypertech PowerProgrammerIII.

 

That's a first.

 

 

 

 

 

 

I love my Hypertech too,Very pleased with it also.

  • 1 month later...
Shu Enthusiast

Shu

Posted
  • Author
Posted
I am very pleased with this Hypertech PowerProgrammerIII.

 

That's a first.

 

 

 

 

 

I love my Hypertech too,Very pleased with it also.

 

 

 

 

 

 

MS3DALE,

 

Did you reprogram your shift points and get your tranny to stop dropping to second with cruise on? Just curious.

 

asilverblazer,

 

Were you not happy with your Hypertech? And why? I know that when I bought mine it wouldn't work right out of the box because they said the dealer had changed something in my computer even before I bought it brand new. After I sent it to them to decode and reprogram, it has worked flawlessly since. I can definately feel the increase in performance and have seen an improvement in fuel mileage. There may be other brands out there that make more power than this one, but I could not find enough solid eveidence of that to pursuade my purchase decision. Just curious why you are not happy with yours.

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted
I am very pleased with this Hypertech PowerProgrammerIII.

 

That's a first.

 

 

 

 

 

I love my Hypertech too,Very pleased with it also.

 

 

 

 

 

 

MS3DALE,

 

Did you reprogram your shift points and get your tranny to stop dropping to second with cruise on? Just curious.

 

asilverblazer,

 

Were you not happy with your Hypertech? And why? I know that when I bought mine it wouldn't work right out of the box because they said the dealer had changed something in my computer even before I bought it brand new. After I sent it to them to decode and reprogram, it has worked flawlessly since. I can definately feel the increase in performance and have seen an improvement in fuel mileage. There may be other brands out there that make more power than this one, but I could not find enough solid eveidence of that to pursuade my purchase decision. Just curious why you are not happy with yours.

 

 

 

 

 

I paid 350$ for a progammer and all I get out of it is adjustable shift points, ability to raise rev limiter (Why would one want do this, I'll never know.), Increase the speed limiter (this is great considering I drive 128 mph all the time now), adjust for different gear ratios and tire sizes (which are all stock for me). I programmed for 91 Octane and noticed no increase in performace, nor an increase in mileage. I should have got a custom reprogram but that was before I knew about them.

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted

No,I haven't reprogrammed the shift points yet,I don't know why,I just haven't done it yet,Maybe I'll toy around with it this weekend.

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