Transmission downshifting with left turn??

[Sando]

My 95 auto has decided that it now likes to downshift when you turn the steering wheel slightly to the left. This at highway speed and just the usual corners in the road is enough to upset the thing... cruise on or off. It just unlocks and downshifts, stays for a moment and then goes back to overdrive until the next corner.
I've had plenty of curly questions to answer over the years but this has me stumped. Any ideas out there?

Thanks, Aaron

 

[Timd32]

Clock spring issuse possible in the column?

I thought Genos carried those, dug for way too long and nothing came up for those.

 

[BigPapa]

Overdrive and TC lockup are the only electronically controlled transmission functions. The OD switch is in the dash, not close to the steering wheel or column. Lockup is controlled by the PCM, again, not close to the wheel or column.

Does this happen EVERY TIME the wheel is turned left?

 

[GAmes]

Does the shifter actually move a mechanical linkage or is it fly by wire?

 

[BigPapa]

It's not fly-by-wire. I can't recall if it's a cable or linkage and I'm too dang lazy to lay under mine to see......

 

[GAmes]

Just shooting in the dark and supposing the steering wheel is moving something that affects the shifting.

 

[Sando]

Thanks Guys for the replys. It's certainly an odd one. It's pretty well consistent that every turn will downshift, or turn off overdrive I possibly should clarify, and not much of a turn either, just highway turns are enough. I don't believe there's any movement in the shifter lever while this is going on. Could there be a way that something in the steering wheel electrics, clock spring or cruise buttons maybe, could cause a momentary switching of the OD switch?

 

[GCroyle]

I know nothing about A/T's. But here's a SWAG.

Motor or trans mount are shot allowing engine to twist enough to shift.

How's that for an uneducated complete clueless idea!

 

[BigPapa]

Here’s your OD circuit. Closest thing I see to the steering column is the “Joint Connector C” that says it’s behind the knee bolster.

Does your truck have Fog Lights? Looks like the Orange wire powering the OD Switch is shared with the Fog Light Switch.

 

[Sando]

Thanks Scott, The OD circuit does seem pretty well independent to everything else hey. There aren't any fog lights. It has to be something electronic in here though. The load on the drive doesn't seem to matter. Under load up hill or easing off over a rise, it's in the turn. I'll have to start pulling things apart and see what I find.

 

[Timd32]

Just stabbing at something outside the cab.

Of course the 8pin on the trans it self, could have some corrosion or needs to be cleaned up.

Also...
My 96 has a pretty large harness kinda below the back of the front fender or just near the front of the door, sorry no pics.

Could it be that there is a harness that has a scuffed wire so when you turn left the harness flexes and opens or shorts out?

From what I recall its a pretty big group of wiring on the left side under the truck.

 

[BigPapa]

Back when I worked at Underwood Tire & Repair, we did all the repairs on the county EMS ambulances. They had a brand new ambulance built on an F-350 or 450, can't remember, with the 6.4L. On occasion, it would completely shutdown when they'd get on an interstate ramp. That's definitely not good for any kind of emergency vehicle, especially an ambulance. Around here, all the ramps are RH turns. The local Ford dealer had it for a month and couldn't figure it out. They brought it to us and we never could figure it out. It was there when I left and the last I heard of it, they were taking it back to the builder.

 

[Sando]

Thought I'd update you all on the outcome. I did fix it by the looks... Added oil! Misread the oil level back at the start of it all and didn't think to double check it. Sometimes we miss the obvious hey.
Thanks for the thoughts everyone.

 

[dieselshadow]

Transmission oil was low? So it was sucking air when you turned? That makes sense.

 

[BigPapa]

So it wasn't really downshifting, just quit pulling? Mine's done that before I found my dipstick tube was leaking. The pickup is on the left and when the level is low, it sucks air when you turn left. It took a pretty aggressive turn for mine to do it. It's definitely not good for the transmission.