1999 limited 4Runner, 3.4L w/ 230,xxx miles :: I'm at a loss of words when the shop I left my beloved at in Hailey Idaho says after minimal testing that it is just a mechanical problem without explaining much in their writeup.

Previous Symptoms: no whirring, clunking or loud sounds coming from shifting, (day of problem) went through tons of puddles wheeling, immediately washed the undercarriage and engine bay clean, drove for around 1.5 hrs at 70mph no problem, parked, then started her up and won't get out of this limp gear, no check engine light or throwing any codes

Symptoms Now:

starts and won't shift out of 3rd gear? (reaches around 30mph at ~3,000 rpm)
goes into reverse fine
transfercase works fine all throughout in 4 high, low and the 4wd button
no check engine light code (or code history after getting it read in the shop)
transmission filter is original since new I believe (pink manufacture gasket maker is what the shop said)
checked all 3 solenoids after dropping the tranny pan and they read ~9-11 ohms each
after asking the shop, they said they checked the wires going to the solenoids for (was it voltage or resistance?) and they said it was fine, but didn't do a writeup on it?
after dropped pan, no shavings, only small buildup on magnets, and no milkshake

Possible next steps:

• Pay $$$ for the shop to disconnect some type of harness to the transmission to manual shift into gears? Forget what its called, but the harness on the outside of the tranny to manually shift it into L, 2, and D?
• Check the ECU that it's sending correct signal down to the solenoids?
• Torque Converter problem? Not sure why this would be the case?
• Replace the transmission :/

Most frustrating thing is that everything was fine up until leading up to it and there is no blaring red light on something specific indicating failure. I'm debating on sending the $300 to fly down back to Idaho to test this myself with my multimeter on a dirt lot. Any help for my daily anyone?

Could be mechanical or electrical - the FSM has complete diagnostic tests to run - here's a couple excerpts.

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