4hi 4lo and od off lights flashing

[Lahey]

My 1999 Ford Explorer Limited has the 4hi 4lo lights flashing, they flash about 6 times in a row, and when you turn sharp you can hear the whining moaning sound it makes. When I try to put it into 4wd it works fine, and the 4hi light will stay on steady the way it should while in 4wd. Also, the od off light flashes, but the transmission shifts smooth and works flawlessly. Except when on the highway, it runs at about 3000rpm doing 60mph... Pushing the od button will put it out of od and then it runs at about 4000rpm.. So the od button does work. I'm not sure whats wrong, or if all those things could be related? I don't think it needs a new transmission, but it shifts nicely and works great, except for revving high on the hwy with od off flashing.. I just bought the truck a week ago.. And it came with a mechanical inspection that was done a week ago and it passed everything..

 

[drdoom]

First thing get the transmission codes read with a good scanner. Another thing you could check, make sure the circumference of all tires match.

 

[Beargap]

That flashing is the error code that there is a fault in the Control Track system. Usually, the GEM monitors front and rear driveline speeds as measured by Hall-effect sensors reading the passage of "teeth" on tone rings inside the transfer case. If the rear appears to be going faster than the front it increases the engagement time of the clutch pack inside the case in 10% steps until the speeds match or at least the rear is no faster than the front. If it gets to 100% engagement, the same as selecting 4WD-Hi, and the rear still reads faster than the front, the system recognizes that this is not possible so it will disable the 4WD and flash the codes. Typically the problems is in one of the speed sensors, sometimes just dirt and gunk preventing a good reading or an outright failure. Not terribly expensive and can be serviced without removing the case. There are other things that can cause this condition, but the speed sensor issue is the most common.