Has anyone had issues with the TBSS 4L60e stock converter locking up between 3rd and 4th?

When driving it goes in and out of 3rd and 4th at 40mph. Could a tune be messing with it? I also noticed that the fluid level seemed high when I checked it the other day. Any ideas?

I know little about tranny's and I am having some serious concerns that maybe its going bad the way its acting but I'm hoping its just lock up and can be resolved quickly, and without going to the dealership.

I have some mods but its an 06 with less than 13k on it.

Any ideas on how to self diagnose?

Thanks,
TXSS

 

If it's going from 4th to 3rd gear at a steady speed, then there is probably something wrong with the tranny not being able to hold 4th. It shouldn't downshift until 37 mph. But IF the tranny holds 4th gear at all other times, then the speedo is off a little and it's at the 37 mph shift speed and the ecm is commanding a downshift to 3rd, then if you speed up a hair it requests the shift to 4th and you get in that 4-3-4 cycle...try speeding up 1-2 mph and see if it's better.