My truck won't drive in reverse or shift wile driving forward

2001 Toyota Tundra 4wd Automatic transmission . My truck drive forward but seem to be stuck in 3rd gear constantly. Also it will not drive in reverse it seem like the e brake is on but its not .I checked the fluid its were it should be. Also when I was driving it , it almost liked slipped out of gear no matter what gear I put it in it wouldn’t move like it was in neutral . but eventually went back into gear. Can anyone give me advice.

What color is the transmission fluid?

Tester

It could be in limp mode although that is usually 2nd gear not 3rd. But at any rate you need a good transmission shop.

Good advice above. When my c4-automatic-equipped truck started acting like that it was in the shop for a complete transmission rebuild within a couple of weeks. Been working fine since. Your goal at this point should be to determine who’s the best transmission shop in town. Ask your current shop techs, anybody you know who’d had major tranmssion work. There’s usually always one shop the car experts take their own cars to. It’s a special skill to run a transmission shop, requires a great deal of diligence to details, and att’n to cleanliness. Conceptually the job isn’t that complicated, its just there are so many parts involved. Whoever your best shop in town is, they may be able to fix it without doing a complete rebuild, but I think you are probably looking some version of a rebuild job there.