I drive a 98 expedition, 152000 miles, and I take care of my baby. Recently the OD light started flashing, and the shift is hard when this happens. My tranny is smooth as silk when not flashing- No codes on the computer, no check engine lights. It's a quiet running SUV. Any ideas why the OD light has begun to flash.

 

Isn't this an indication that the vehicle is in "limp home mode" - normally due to a transmission fault? I think a bad solenoid body is usually the cause in these trucks. On a couple of occasions the blinking OD light happened in conjunction with a transmission overtemp condition - a crapped out torque converter was to blame there - but they might not have been related directly. Either way, transmission problem.

 

The computer is telling you that you need to have the trans checked by a qualified transmission mechanic or shop. Something is either bad or will be soon. Just be careful in where you go as there is a lot of Mumbo-Jumbo in transmission speak that the average person does not understand and there are more than a few rip off artists out there. I personally think the best option, if your trans needs rebuilding is a Reman from Ford as the warrantee is nationwide for 3 years or 100,000 miles, the last I heard. The Ford Remans will have all the latest upgrades and the warrantee is good even if it is not installed by Ford as long as the truck is brought in for an inspection after the job is done to insure the job was done correctly. Verify what I've said with a Ford Parts person to be sure.

 

Thanks for the reply, but no limp mode.

 

Thanks for the reply;
Thats the thing it was checked by a mechanic, a (real) one, not the back yard kind.
Still no codes, but I really don't want a new tranny.
How come the tranny is not slipping if it is going bad? That is what confusing me, I've been in cars with a bad tranny, and it's not a pretty sight.
I'm going to have to let my mechanic take it to a tranny guy. Any other idea's of what it could be beside the big T.

 

Wow, this has raised a holy hell of conflicting opinions among my friends tonight... everything from water in the PCM to bad speed sensors to a torque converter overheating.

First, one of the guys mentioned something about the OD light flashing codes, separate from the OBDII codes. There's a separate computer for the transmission and it transmits fault codes via the O/D light. Does it blink in sequence? If so, what sequence does it blink if in a sequence at all.

The suggestions among 4 mechanics over beer and pizza tonight are:

1). Check fuse 23. Wiggle it around, make sure it's in tight and not melted. If that's shorting out or loose it'll cause unholy hell.
2). You have a flaky GEM module, probably water leaking into it. Many 97-10 Expeditions get the dreaded "bottom of the windshiled" leak which conveniently fills up the computer with water.
3). A short in a wire in the control stalk.
4). Bad speed sensor at the tail of the transmission (but he thinks this is an Explorer problem)
5). This requires a follow-up question: Does the blinking happen more frequently the longer the truck has been driven? If yes, the transmission is overheating, probably a bad torque converter. That hard shift is the torque converter failing. Torque converters will sometimes only start to show failure under load and when heated up. There's no trans temp gauge on the Expy, so you're not going to know it's cooking itself to death until the transmission fails suddenly.
6). You've got a bad solenoid somewhere in the transmission that's not working within tolerances, probably only after getting heated up. Look here... http://www.alldatadiy.com/techtips/Ford/20050317d.html Again, though, this will not dump an error code to the OBD II. The error code only goes so far as to blink the OD light with a code.

 

Your the man! Thanks for bringing my truck up in convo.
Ok I pick number 5. I drove it about 25 miles one way on Friday and it didn't blink once, I let it sit for 2 hrs, and on the drive back home after about 5 miles it started blinking. The blink is just like a turn signal blink, no sequence just constant. Right now a TC sounds a little less expensive than a Tranny, but I will wiggle fuse 23 before I head out today.
I will keep you updated on the outcome. Thanks again~
PS..Happy Thanksgiving

 

Torque Converter Clutch Solenoid failing, most likely. Happened to me last summer. OD light started blinking, truck would shift really hard and then stall. After doing alot of research and having the code pulled I was able to replace the solenoid myself. Dropped the tranny pan and replaced it.

 

Update:
It stop flashing three days ago..??? and I took it to the tranny shop, they couldn't pull up a code.
My mechanic is thinking TC clutch slippage, or solenoid. We'll know in a couple of weeks, droppin her off at the shop.

 

I personally think that's what it is. After all the research, it pretty much points to that.
I will def let you know.

 

Was it the TCC solenoid? How much did it cost to replace that (sorry I am having a similar issue so I am curious)