Wont go into overdrive

Trucks a 2000 Tundra Sr5 4wd with 4.7
Truck aint going into overdrive.

Ok so here's my problem, my trucks acting like it was when it was pure ice and snow out.
Not shifting down when I put it into 2 and L for engine braking.
No overdrive. So I hit around 3-4k when going around 60pmh
Shifts at super low rpms even when foot is to the floor. Only way to stop it is choose L or 2 to keep rpms up
It has done it 2 or 3 times since the last snow with was a month ago.

Any ideas? Comments?
Any help will be amazing or links to previous threads on this.

 

After filling it to full when it's warm, if nothing changes (if it does change, find where your leak is) I would get the transmission fully flushed at a place that uses something that utilizes a cleaning agent like this...

https://www.bgprod.com/catalog/transmission/bg-quick-clean-for-automatic-transmissions/

If that doesn't work, I'd go the solenoid route mentioned below...the flush will probably cost your $100-200 for an A340F...so even if you have to go the solenoid route
you should be in the sub $300 range.

 

long shot, but have you unplugged your battery to reset the "brain"? it sounds like it could simply be a control issue.

 

I would change fluid out. See what the old fluid looks like, and be sure to have the fluid level right. If the fluid level is off by even half a quart it will act up. I was once a little under half a quart low after changing my fluid and it wouldn't get into overdrive at all. Topped off and the problem went away immediately.

Good luck, let us know what you find.

 

Double post

 

Ok thanks everyone. I'll reset the "brain" tommorow after work if I have time. It has gone away today.
It does seem like a off and on problem.

Plus a tranny flus wouldnt be a half bad idea because I don't have any service records from previous owners and its at 230k miles now

If none of this fixes it ill go with the solenoid fix

 

Just a suggestion based on your additional info here: Do a full transmission service by dropping the pan which will allow you assess the transmission health. Clean out the pan and install a new screen and solenoids before the put back. They sell a screen and solenoid kit for our trucks. Make sure you use the Toyota Transmission FIPG (form in place gasket).