If it's not one thing, it's another ...Dang!! Are the RPM's going high? Does it seem to slip in high gear, or all gears? Have you replaced the fluid lately (that could be the prob)?
1) I guess if it were mine, I'd first check the trans & vehicle for any codes. You never know. Obviously the fluid level/quality ..which you've probably done.
2) If you've replaced the fluid lately, that could be part of the problem. Something to do with the filter/seal, etc, perhaps. Try a different brand ATF. Coefficient of frictions could be different with what you put in causing the clutches to slip. I've personally had chatter happen with one ATF and go away after changing to another (in a GM pickup).
3) Could take it to a trans shop and let them check pressures, etc. Get a professional assessment. There are a lot of troubleshooting points they can do and pretty much drill down to what the problem might be. Might be the torque converter and not the actual transmission (??). IDT a sensor issue would cause that, but I can't say for 100% certainty.
4) Worst case, last ditch effort, if $$ is tight, you could pull out some tranny fluid and add in a can of
Trans X or another tranny miracle product. Trans X some say is the best (??). Try to coax it to life till you get some $$ saved. My brother had a car many yrs ago, which wouldn't even move under it's own power. Put in a can of Trans X and followed the instructions ....waited quite a while like 20 minutes, maybe 40 ....and darn if it didn't eventually start to creep forward. Ultimately it came to life and he drove the car for 3 or 4 months. The tranny acted fine. He sold it to a guy and after about a year it crapped out. But he DID extend the life of the tanny. ...not saying that's a recommended way to go, but it's *a* way, esp if that's all ya got... Or get a used or rebuilt unit if yours is known bad. Or have a trans shop rebuild yours with all the latest updates.
Let us know what you find in terms of codes ...and way forward.
