O/D Problems (light didn't come on)

[MustangP51]

For the last year my transmission (4r70w) has been shifting hard every now and then. It will have a few good shifts, then usually when it downshifts from 4th into 3rd while under a load, and at a low RPM around (1500) the will be a very hard shift. I had it looked at my friends shop, couldn't find a problem, and the fluid was changed, flushed and replaced with Mobil 1 ATF. That was about 9 months ago.

Now yesterday while driving I pushed the Overdrive button on the end of the shifter and the O/D Light did not come on in the cluster and would not turn off the overdrive. Pulled over shut the engine off, restarted the engine O/D indicator light still refused to turn on, and the overdrive refused to turn off. Got the thing home. Let it sit over night, and in the morning it was fine. The overdrive light was working and the overdrive could be turned on and off.

I am at a TOTAL loss for what could be the problem with the transmission. I can break down any other component of a vehicle in my sleep, but automatic transmissions are like alien technology to me.

What should I do at this point? She is not moving until this is sorted out.

 

[CPUNeck]

The O/D switch could be shorting out in the column. I know this is a big problem in the F-series trucks. This can cause lots of headaches, don't know how much $$$ it is to replace, but probably not much. (The whole shift lever with switch and all for my F-250 was only ~$35.)

 

[budwich]

You should be seeing 12v on the T/W coming out of the steering (from the o/d switch).... that's what the switch "sends" to the PCM to get it to "do something" with the O/D. Get a meter, and see if you can "see it" with just the "key on". If not, then you might have a bad O/D switch or broken / loose cabling going thru the clockspring. The BAD part is that if you see the 12v, then you probably got "bigger" problems related to your "symptoms" that you described at the start.

 

[parad1mg]

check your headlight switch.. i had the same problem and the headlight switch was the cause.. turn the knob and make sure it is functional and return it to the off position.. i'm not saying this is the source in your situation but it's a 1 minute check and see and its free..

 

[CPUNeck]

How can the headlight switch effect the function of the O/D switch??

 

[budwich]

I think what para... was thinking was that the light wasn't working... not thinking about the actual function of "no O/D". Some of the warning lights get their power from the headlight switch... O/D is one of them. So if the switch is "broken" then it is possible that the light won't turn on... HOWEVER, the "turn off" function on the tranny is not related to this problem (ie. headlight switch).... which I think is indicated by the poster that the "pushing of the button" had no effect on the actions of the tranny.

 

[CPUNeck]

Wow, there is some engineering at its best, you can dim and indicator light out. If I'd of designed it, you could dim it, but in the event of a dimmer circuit failure, it'd go back to full brightness