above 45 mph the rpm’s will jump over and over, the transmission shop says nothing is wrong with the transmissionany ideas ? it does this wather the over drive is on or off.
I’m assuming you see it in the tachometer on the dash, but do you feel the engine revving up and down like that? Also, will it do this if you drop the shifter to 3rd gear?
i dont really feel it as though the engine is accelerating. and i have not tried it in third gear. the truck is a 01 dakota sport quad cab 4x4 with a 6 cylinder engine. it feel like its looking for the 4th gear or overdrive. the tack jumps by maybe 100 rpm’s. it doesnt seem to matr if the od is on or of.i wish i could give more info thanks i dont thinks its just the tach. i can hear the engine speed pick up slighltyas if its trying to up shift
You may simply have a bad tach. I replaced the one in my Ford Explorer after it began acting strange. It would drop 500 rpms on a whim, restore back, and sometimes drop to zero. A sharp rap in the dash would stop the bouncing.
I yanked a dash cluster out of a junkyard Explorer and swapped out just the tach unit. Haven’t had a problem since.