transmission Q's

[highmtnyukon]

Hi-
New to the forum. I have a 2005 Yukon SLT w/ 32K mi. I use the truck mainly for towing my 3500 lb. pop-up for camping. It works well, but when on the highway at 70-75, when I get to a hill, the tranny often downshifts to 3rd and then immediately to 2nd (4500+ rpm!). This also happens occasionally without the trailer. I live at 7000' in the mountains and drive over lots of passes, but it is annoying that the tranny downshifts so quickly. BTW, this mostly happens with cruise on. Is this typical, or is there an issue with the trans electronics? Other than this issue, the truck runs perfectly. Is a programmer the best (or only) way to change shift points?
Thanks!

 

[Sepiroth]

You kinda guessed it yourself. When you use the cruise, the cruise will try as best it can to keep the vehicle going a certain speed. If it involves the engine to speed up then it will automatically downshift the trans to the right bear to get the heft moving to keep the speed constant.

I bet if you were to do this w/o the cruise on you will find that it will take more pedal to get the truck to go up the hill too.

Does your truck have the tow/haul button. You can prolly use that button when you are towing.

 

[highmtnyukon]

Thanks for the reply. I guess I wasn't clear about the issue. When towing (and sometimes not) with the cruise on, the truck downshifts to 3rd, but immediately again downshifts to 2nd. Maybe I'm being too picky, and it's just the way it is, but it seems that speed could be maintained in 3rd. Are there programmers out there that allow me to adjust shift points/perameters? I am in tow mode when pulling the trailer BTW, which makes the truck downshift to 2nd even more readily.

 

[M.M. 700]

Mine will do the same thing on a good hill, if I run the cruise. I also have a 2500 HD 6.0, and it will do it to.

There are proramers that will let you adjust shift points......just be careful how you set them.....if set to high it could put more stress/heat in the tranny.

 

[boostaholic]

You can get a tune but that little 5.3 is gonna be working hard up the passes. A good tuner can get you a solid tow/haul revision that won't drop to 2nd unless you stand on it.

 

[highmtnyukon]

Any recommendations on the tuner? Are you talking Hypertech or similar or an actual person modifying the shift points? I'd sure like to eliminate that downshift before a piston comes through the hood!