I just bought a 90 F-250 with a 5.8L engine and a E4OD auto tranny. The
tranny has just been rebuilt and installed in the truck before I picked
it up, and on the drive back, the speedometer seemed a little off - in
fact I covered a measured mile in 60 seconds with the speedometer pegged
at 70MPH - so at that point it was off by 10 MPH.
Since the speedometer is not electronic on this vehicle, and is
obviously mechanical, any suggestions on how to get the speedometer to
get more in synch with the actual speed?
Sounds like they used a different speedo gear than you need for the
tires/axle ratio you have. This may be due to a tire or axle ratio change
in the past or just using the wrong gear when they rebuilt the tranny. Take
it to the rebuilder and they should be able to change the speedo gear in a
few minutes time.
It sounds like you have the wrong drive gear in the trans.
If you know exactly how much off it is percentage wise, you
can get another drive gear from Ford. Before you ask for a
new one, pull the old gear and note its color and number of
teeth so you know what you now have. Also, get you trans
code off the door decal. If your speedo is 10% high, get a
gear with 10% more teeth. You don't want to get one larger
than needed because the speedo will then read too low which
may get you a ticket. For instance, should you calculate
you need a 16.75 tooth gear to be right, go with the 16
tooth. Better that it is a bit high. Removing and changing
the gear is a basic operation requiring only one wrench and
possibly pliers to loosen the cable collar. You won't lose
any fluid to do this. You may need a new Oring for the gear
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