Back in 2019, rust ate thro' transmission line to rad ( 2005 V8 AWD ) and there was a "gradual" loss of fluid. Did not noticed fluid loss due to all roads to/fro our house are gravel country roads/lanes. Initially noticed the odd clunks from tranny when coming to a stop or starting out. Should have started doing tranny checks, but did not, since noises did not occur consistently. Within days, wife went into town for groceries and car came to a complete stop on return trip just about a thousand yards from our place. Towed it home and found broken line and zero fluid left in tranny pan. A $4200 complete rebuild later by tranny shop ( new planetary gears, bands, torque converter etc. ), and she was back on the road. A costly lesson !
I echo AuSeeker's advice. Check fluid level immediately.
Toyota tranny is a sealed unit with no dip stick to check fluid level. Check must be done from under vehicle. Jack up vehicle for more room if you're a big person. You'll find a 24mm bolt/plug on passenger side ( about 2/3's up ). This is the fill plug. Two other plugs at bottom of tranny pan. One is a drain hole and the other is connected to an overfow tube. Add fluid from fill hole till fluid flow out of this overflow tube. You'll have correct fluid level in tranny ( vehicle be as level as possoble). FSM also says to do this with ambient/fluid temp at certain degrees to be completely exact. Its overkill IMHO unless you 'er doing this work lying on a garage floor in -20 degree weather. Tip: Make sure you can get fill plug open before messing with drain or overflow plugs. Good luck.