trans problem output shaft revoloution

I have slow engagement of overdrive on my 01 4x4 diesel It takes 7 miles before it shifts overdrive then is fine unless I shut it off for 1 hour then I have to drive 7 miles again. I had the trans scanned and it came up that there is no revoulition output being scanned does anyone know is this picked up form the differential sensor? Or where is the pickup for output revoulition There are no wires or sensors on the transfercase but there is one under the overdrive housing. Computers BA! HUMBUG! can't live with em and can't live without. But sure would like to try

There's been other posts here about auto tranny problems when the speed sensor goes out. I'd try replacing the one that's bad, obviously the trans isn't getting the data it needs to do the shift when it's supposed to.