Re: 2005 Ford Explorer O/D light flashing
Take it in to see what codes are coming up. Transmissions can have specific codes; similar to an engine that tells the shop more directly where the problem lies. It may be something as simple as a bad solenoid. Also, before you take it anywhere, make sure the fluid level is correct.
In most cases with automatics, when you get low (really low) on fluid, you won't be able to grab any gears; you'll place it into drive or reverse and the engine will just race without you moving. It'll be the same as if you had the transmission in neutral.
If there is no harsh shifting changing through the gears, chances are the transmission itself is OK. The torque converter may be the culprit.
When you drive it next, manually keep it in 3rd gear or if you can, lock off overdrive and see if the light still comes on. This can help the diagnosis a bit when you take it to a shop. More importantly, if you explain to a shop/mechanic what you've tried to alleviate the problem and do a self diagnosis, they'll be less likely to rip you off thinking you know almost as much as they do.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!