Ford E350 (1992) with automatic transmission problems

[Little Indy]

I have a Ford E350 diesel (7.3) with an automatic transmission and overdrive that I use to pull my 16 foot trailer on which I place my cubs and implements. The transmission was overhauled about 3k miles ago and on a recent trip from NE to State of WA and developed an interesting problem. We made it back. No problems if we leave it out of overdrive (but it gets about 3-5 mpg less). We pulled a 2k lbs camping trailer there. In overdrive the off light began to flash (about 50 miles) and continued to flash until we stopped for a short time(about 15-30 minutes). When flashing the van shifted roughly and the engine surged for a short (1-2 minutes) time. On the trip back (no trailer) if we put it in overdrive after about 150 miles the same thing occurres. We did not even try overrive in mountains with their 6-7% grades and their ups and downs. One long 6% grade had a 25 mph speed limit and sharp curves (engine braking is nice). The van has a transmission cooler that seems part of the radiator and an additional add on cooler. I checked the fluid levels on several occasions, and each time they seemed ok. The fluid looked pink when checked. The van drives fine all day in NE, in ID, MN if not in overdrive.

Any ideas appreciated.

You guys and gals in LA&MS are in my prayers and donation to be sent.

[WKPoor]

Todays trannies are very sophisticated with electronic shift and all.

2yrs ago we went to florida in a Bonneville and had tranny trouble about 1/2 way down and all the way home. After we were on the road for a while the tranny would down shift its self to drive and stay there regardless of selection.
The problem ended up being self induced. I overinflated the tires. Tire pressure on the tire said 40psi. On the door it said 30psi. I aired them to 40. That made the tire a little bigger around. The ECM monitors wheel tach speed though the antiskid system and compares that to the engine tach. If the ratio gets to far out the ECM assumes you having tranny trouble and protects itself by locking out overdrive. Now go figure!

[Marion(57 Loboy)]

My sister in law has a Ford pickup that did that while she was returning from out of state while towing a horse trailer. One guy at a place she stopped off at in Indiana scared the crap out of her with a guess at what was wrong and an outrageous estimate for repair costs.

She took it where I recommended, and it cost only about 145 dollars for a sensor replacement.

Hopefully that is all that is wrong with yours. My advice is: ( in addition to be being free ! ); that you take it to a dealer or other transmission shop that has the latest in computer diagnostic equipment. Today's trannys last a good long time if maintained properly....it's the electronic stuff that fails more often than not now.

The days of your tranny having only a vacuum modulator to worry about are looooong gone I'm afraid!

[Little Indy]

Thanks Guys!
I took The Great White Whale (white Ford E350) to a specialized tranny shop and had them check the codes. Turns out it could be a sensor malfunction (a 40 dollar fix) or iy could be in the wires in the dash between the sensor and the computer a 400 dollar fix. I could to try the 40 dollar fix first. Hope the best. Thanks guys