My Dad has a 2000 F-150, 2wd, 6 cyl with a 4R70W transmission and about 250,000 KM (155,000 mi) and as far as I know, the fluid has never been changed, he bought it with 190,000 km
The transmission has lost 3rd and OD. From a start it will go from 1st to 2nd then it will neutral out and the rpm's shoot up when it should shift to 3rd, never engaging.
If I push the OD to lock it out, it will then start in 1st and shift- then stay in 2nd.
There is some engine braking in 2nd gear.
The transmission was overfilled by about 1.5 Liters by a relative which I checked first,and have since sucked out.
I am curious if this might be a stuck solenoid (SS2) caused by dirty fluid and overfilling or a worse problem such as the direct clutch pack. There are no codes that I can read with my AutoDiag scanner by DiagTek and the OD light is not flashing.
I don't know if it's worthwhile crawling underneath the truck and dropping the pan, changing fluid and gaskets etc if the transmission is shot.
Any help is appreciated,

 

So, I figured I would drop the pan and check it out. The magnet was about 3x it's normal size, fluid dirty, filter looked bad and the dipstick plug was still in the pan.
Checked SSA and SSB both clicked when commanded, so I dropped the valve body anyway and cleaned up everything.
$100 for filter and fluid, floor covered in transmission fluid and now I know the transmission is shot.
But, for all the issues others have had with the 4.2L 6cyl and 4R70W transmission this truck has over 256,000 KM (155,000 mi) with minimal maintenance original fluid and filter, plus I know it was driven hard for the last year.