When I turn my overdrive off on my 99 auto, I'm running like 4000 rpm and going 70 mph with no sign of a next shift in sight. Is this normal? Is my tranny acting right? If this is normal, what range should I expect a shift? I know this question might sound dumb, but this doesn't seem right to me. I still got plenty of warranty on car so I wanna get it fixed now if it is something wrong.

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Yes, that is what it will do. When you turn of overdrive, you are turning off the last gear(your high gear). It will not shift any further until you turn it back on.

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