i have a 00 ford expedition 4X4 with R100 trans and 3.55 LSD.
the problem is my O/D light on my gear shift **** just started blingking on and off.i started feeling around my gear as it shifts and it still goes thru all four gears.wondering what could be the problem.it just started 2 days ago and its been fine before that.first time it ever happened to me.
anybody have an idea?

 

It's like a "check engine" light, it's an error code.

 

You need to have someone read the codes to find out what's wrong. The places that say they read codes free usually don't have the right tools to read a Ford trans code. Their tools will say that there are no codes. That's not correct. If the light flashes a code is stored in memory, and it will stay there for about a month.

 

thanks guys.ill do that.
one more thing....i drove my truck tonight just to get a feel of what else is going on and i noticed that 1st to 2nd gear shifts just fine then 2nd gear will run,when it hits the shift point,the RPM will drop maybe 500RPm from the shift point then continue the 2nd gear again.when it reaches the shift point again..then itll go in to 3rd gear(i can see the big drop in RPM so i know 3rd gear is engaging)the at the next shift point,itll go to 4th gear or O/D.
weird..it feels like a have 5 gears but the 3rd gear(really the 1st shift of 2nd gear) just goes thru like 500RPM.
anybody ever had this scenario?

 

I think it might be locking the torque converter.

I'm not sure about your trans, but in my truck the torque converter will lock in 3rd gear if it isn't under heavy stress, giving the feeling of another gear when it's actually not. The RPM drop is about 500 give or take a few for mine also.



For you guys that know more about this than I do, please correct me if I'm wrong.

 

went to autozone today to get my OBD2 read and the guy told me this...

P0755
definition=shift selenoid2 circuit condition
explanation
ECM energized selenoid and detected an open or short condition
probable causes
1.open or shorted selenoid
2.open or shorted circuit condition

the truck has a tune and is supecharged and NOS.
it was tuned on a 2 wheel dyno.i pulled the fuse that enables the 4AWD.it was tuned past summer and never had a problem with it until 2 weeks ago,i just put the fuse back in for winter snow.
i friend from midas read my OBD2 a week ago when my check engine light came on and told me that the selenoid kicked in and thats whats causing the check engine light but the gear shifter O/D wasnt lit at that time.
does this really pose a big problem as far as my transmission getting screwed in the long run?
or..should i just leave it alone?
also...im not sure if all the codes were read properly since mark kovalsky(see 2 post up) mentioned that some stores dont have the proper tool to read ford trans code(do ford use a different OBD2 reader?)

 

Ford transmission codes MUST be read by a Ford specific reader. Any code that turns on the Check Engine light can be read by any OBDII reader. Autozone was able to read what turned on your check engine light. There might be another trans code stored.

 

I Got a 97 F150 and the Od light started blinking just going down the road and now it wont shift into any higher than 2nd gear would that be one of the sensors?

 

Its in failsafe mode and you need to get the transmission codes read.

 

where are the sensors located at on the truck and how can u get them off?

 

You take a look at the side of the transmission where a bundle of wires run into the solenoids and whatnot and use the proper tool to get them out....AFTER you have gotten codes checked and figured out what is wrong.

 

My overdrive light was flashing and all it wound up being was a connecter loose going to my transmission. Check all your wire connecters to make sure they've not jarred loose. Hope it helps...