The tachometer sensor may fail; if the tachometer needle jumps around and the transmission has harsh shifts or does not upshift, this sensor should be checked. This sensor is mounted in a cover at the front of the motor.
Average mileage: 141,206 (100,230–167,000)
Drive Trains affected: 2WD, 7.3L V8 Diesel, Automatic Transmission, Diesel
10 people reported this problem
Tachometer jumps around, even going to zero, causing irratic down and up shifting of the automatic transmission. Very disconcerting.
my tachometer quit and I have noticed a difference in when the transmission shifts.
I replaced the the tach sensor but the problem still persist could I have an electrical problem with the fuse box , wiring, or something else. I am at a loss.
I have a 7.3L and the tachometer started dropping down and becoming erratic (after the engine heated up)then 1800-2000 rpm sometimes it becomes rock solid. So I bought a new sensor from Ford Dealer and I'm about to install it today. This circuit uses a HET (Hall Effect Transister) type pick up and is probably breaking down under heat. It does seem most people have the problem begin around 160,000.