Might be a good time to do a trans service. New Filter and Flush the fluid. Did you drive it long enough to get it good and warmed up and it all drove just fine the whole time while cold and warmed up??? If so, it's very probable, either the Governor Valve was hung up with a piece of junk in it, or a valve in the valve body was hung up. Whatever could have had the valve hung up, is now dislodged and it's working OK. But, that's a sign there is some junk making it's way thru the trans and you should try to get it before it repeats itself.
Also, make sure your TV cable is free and not getting stuck or has any kinks in it. Sometimes you can throttle to the floor, the TV cable comes all the way out, then when you let off the cable stays out, telling the trans you're foot is to the floor so delay the shift long as possible before shifting therefore it won't shift until the governor overrides the TV valve and allows the shift.
