Re: 99 Taurus SE transmission - dropping out of gear again
You can try a trans flush, but that might cause more harm than good. By the sounds of things that you had new fluid added, and the problem returned tells me that the internals of the transmission gears are more than likely glazed due to an overheating problem that you might not have known about...
When you drop the pan, check out the pan itself for any small metal particles or anything that looks like metal dust. If something wore out or broke that's small enough you might just be getting away lucky at this point, and new fluid on a regular basis is only putting off the inevitable - a rebuild. Heat is the ultimate killer in automatic transmissions. Once the clutches glaze there's not much one can do and I'm sure this is what has happened in your case. You might get away with just replacing the clutches, which still involves tearing down the trans unfortunately.
"Hardened seals internally", ask them how they know this to be the problem? Did they shove a small camera in there with a light and see this for a fact? Demand that you be told how they came to that conclusion as it seems like a wild guess.
You might want to scan the vehicle for codes, even if nothing came up, it could've popped on for a second while you were looking elsewhere and the light went away. If there is something stored in the PCM you should at least check, as it can greatly narrow down your problem. Who knows... it could be a sensor that's just causing electrical/hydraulic problems with the transmission.... never know!
'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!