I lived in Yosemite last summer (good experience) and I used my downshift button to prevent kickdown. Probably my kickdown cable was too tight, but on the really step ascents (there was no flat area for the entire 32 mile drive to the foothil town where I bought my groceries) I was kicking in and out of overdrive every few minutes. This gets to be hard on the trans and I decided to just leave it out of overdrive. I never had any problems. I also used it on the downhill portions exclusively.

On the highway, I never use kickdown above ... well, actually I occasionally use it as high as 70. 3rd gear on the AW 7x trans is about a 1.2? ratio, and even at 70 my rpms are maybe 3500?

For mountainy driving (about 4000 ft up/down over each 12-15 miles), the OD lockout was the perfect solution. The catch, however, is that I never exceeded 45-50 on the downhill stretches. The turns were too long and dramatic to go very fast, especially on a weekly commute ;)

I think the #1 killer of kick-down cables is lack of lubrication. Each time you accelerate, the kickdown cable does move, but not necessarily enough to cause kickdown.

-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond