2nd Gen Tundra Trans Slips when cold - only after sitting a while

2013 Tundra, 2nd owner. Original owner did some some towing with it but not sure how much. It's been serviced 100% at dealer and very clean.

When it has been parked for a few days or especially for over a week, when I first start it if i throw it in gear immediately it barely moves at all. Forward/Reverse doesn't matter. Once I wait about 1 minute it will move and wakes up and then works fine within a couple of minutes I'm driving.

• I don't think there is a connection to outside temperature.
• No leaks.
• 72k miles on it and it has done this ever since I bought it at 65k miles.
• I had transmission flushed and synthetic fluid replaced a couple thousand miles ago, didn't make it any better or worse after it's been sitting.

I found this on a Ford truck forum but it sounded similar to my issue.
The problem is most likely the leakdown check valve for the torque converter is leaking. The ONLY problem that will cause is that the transmission will appear to be slipping for a while after the trick sits for a while. It isn't slipping, it is the torque converter that temporarily becomes a high stall converter until it fills up with fluid again.
The way to diagnose this is to check the transmission fluid level after the truck sits long enough to have the symptoms. Check the level BEFORE starting the engine. If it is really high it's because the converter has halfway drained into the pan.

Any insight is greatly appreciated!

 

I had this issue after I changed the fluid. Long story short, It was low on fluid by about a quart.

 

Thank you, I'll warm it up and check the level closely again.