1994 F250 O/D light flashing

[nixter]

Hi all - newbie to the forum and already I have a recent problem that cropped up.

This is the issue with the dreaded transmission OD light causing hard shifts, etc.

I've read thru the forums and found some tidbits of info; however if anyone out there has experience and can pass along their knowledge it would be highly appreciated


The truck:
- 1994 F250 4X4 longbed, super duty, extended cab, IDI Banks Turbo "K" engine, Automatic OD transmission

The symptoms:
- Transmission works fine when first starting in the morning - shifts smoothly and all is good. Within anywhere from 30 seconds to 3 minutes, the system goes into "O/D flash" mode (a limp mode as I understand it) and the 1-2 and 2-3 shifts 'bang' into gear.

The questions:
- Apparently there are trouble codes stored - can these be accessed via the standard OBD port - or is there a separate port available & scanner needed for tranny problems?
- From what I have read - I should start with a trans fluid flush to start - the fluid is a little cooked already so it can't hurt
- Is there a FAQ on this issue somewhere?

Any and all knowledge is appreciated in advance

Thanks!

[nixter]

Well I think I found it - and I am posting for any others who may have this problem.

After some forum surfing I found that the tach sensor can be the culprit. As a test, I observed when the OD light would start its flash routine and saw that is was when I was in the mode of slowing to a stop.

The tachometer reads zero revs at idle and the connection to the tranny issue did not click until just now. I am guessing that as the truck rolled to a stop and I took my foot off the throttle, the speed sensor (rear axle?) read forward speed but the tach showed zero - this must have freaked out the automatic trans computer and set the O/D light error.

I bumped the idle so the tach would read something and took it for a second drive - problem did not crop up.

Ordered the sensor at the local Ford dealership for about a hundred bucks. Not a bad bad price overall...

Keep on truckin'

[ipz2222]

"not a bad price",, unless you know they used to be $39.

[Tyler]

Glad you got it fixed, I had the same problem few years ago when I changed the fuel bowl on it and dumped 1/2 gallon of diesel fuel down the back of the motor and fired it

Was neat tho cause when you'd floor it, it will chirp gears through all 4