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[cdnsarguy]

A dead tach sender should/would send the automatic trans into a "failure management mode" (limp mode) with harsh engagements and firm shift feel and an abnormal shift schedule. It has no effect on a manual trans only the Tach readings.

Check the wires where they exit the big nut on the oil filler housing , known to short out due to bare wire.....

Replace the tach sender on the oil fill housing a big 1" nut with 2 wires. Ford only part Engine RPM sensor E5TZ-17B384-A about $50. You can remove and clean it but usually changed later too.

You can test it too, hold it in the air away from ferrous metal, using an ohm meter lead on each wire you need DC resistance between 2000-3000 ohms.

When the FSV (fuel selector valve) shifts between tanks the last thing completed is the fuel level senders info..... You could try checking the connections at the FSV and the tank.....

Here are the fuel guage test #s (93)

22 ohms sent to the guage it reads empty "E"

145 ohm sent to the guage it reads full "F"

Here are the sender test #s

Sender at empty stop 14-18 ohms

Sender at full stop 154-162 ohms