tranny downshifts for no reason
 

I work w/ a person that has a tranny question:
vehicle: 2000 Expedition 5.4L, 124,000 mi
Turned the air on full blast yesterday...ran a little rough...shut AC off. Was normal driving and the truck started downshifting periodically while driving for no reason. ATF is full and changed recently. Dont know if this is related but lights on dash lights and overhead compass/therm. seemed dimmer and the compass/therm. would flash on and off.

Thanks in advance

I just drove the truck, and it first it seemed like the torque converter was locking/unlocking while driving at a steady speed of ~50 mph. The tachometer would drop to 0, spike high, then settle again. This was not representative of the actual RPMs. Driving a little more, it seemed like it the engine would bog down when the funny shifts would occur and the tachometer go crazy.
Any Ideas?

Fix the engine problem and the trans problem will go away. The trans is just a symptom of something else going wrong.

Have the codes pulled. Somethin up electrically...

Adrianspeeder

Actually, don't think it is an engine problem or a tranny problem. We disconnected the battery and let it sit for a few hours - I went back reconnected the battery and drove it. I agree with adrianspeeder that it is an electical problem - possibly related to the VERY corroded negative battery cable/battery post. It is so corroded I was I couldn't loosen the bolt to take the cable off of the post - I had to disconnect the positive cable.

Oh yeah, the check engine light is NOT on.

Get that ground cleaned asap

Adrianspeeder

Apparently the alternator crapped out last night on the way home. The gauges pegged, the windshield wipers came on, and the truck died. After getting jumped, it reportedly ran a few seconds after the cables were removed and died again.

I'm guessing between the alternator getting replaced, the ground getting cleaned, and replacing the battery (still the original), the problem will be solved.

Thanks.

The alternator was replaced, which helped some. It was still acting funny and ended up throwing a code - misfire cylinder #3. The plug and coil was changed and it seems to be running fine now.