I had to replace the engine in my 99 Ranger 4x4 3.0L auto because of a cracked head.I got a good engine with low mileage and all is well with the new engine.However the O/D light starts blinking soon after I get up to road speed and I get a real harsh shift in and out of first to second gear.If I shut the engine down it will go through the same sequence and I won't get the light again until I get back up to road speed.

I like to ride the dirt roads and usually only go 10-20 MPH while doing so and the light never comes on.

I don't have access to a code reader,but this is a new problem and I'm trying to figure out what happened in the engine swap,if anything,to cause this problem.

The transmission works fine up until the point of the light coming on.I have O/D and all gears as well as 4WD low and high,just a harsh shift down from second and up from first.

Got any ideas??

 

The symptoms you describe are often the result of a bad ABS Speed Sensor which is mounted on the rear differential. Not that expensive and fairly easy to replace yourself.

 

My 94 Taurus did ths rough up & down shift thing, betwen 1'st & 2'nd & it turned out to be a misbehaving speed sensor.

My Cruise Control would also drop out when it acted up, or sometimes I couldn't get it to engage at all. Are you having cruise control problems too???? If so it's a clue to suspect the speed sensor circuit.

My speed-o wasn't afected, as it was cable operated & the speed sensor was just driven by the cable & it's output fed the other things separately.

Anyway the Rangers speed-o, uses the electrical output by the speed sensor, so are you seeing any irregularity in the speedometer???? If so it's another clue to suspect a problem with the speed sensor, it's wiring, or electrical connector.

Seeing as how you said you like to "ride dirt roads" & the speed sensor & it's wiring are located atop the rear pumpkin, seems to me another reason to check it out.

I had to drive the Taurus with my scantool atached, to catch it's speed sensors output "hanging up", between 30 & 35, then "jumping" up or down, dpending on whether I was accelerating or slowing down, & this was right at the trannys up or down shift points & it'd GRAB second or first gear really hard sometimes.

It's output was normal at all other speeds & the computer never lit the CEL or stored a trouble code.

I just had to be monitoring the speed sensors output at those speeds, to catch it. Replacing the sensor, fixed the hard shift problem.

Good idea IMHO to have the computer scanned & see what clues turn up.

Let us know what you find.