I take it you added the trans temp guage? Honestly, I don't think 230 is bad at all.
FWIW, your trans will drop out of OD if it gets to something like 265 degrees to protect itself.
But with that trailer, which is roughly a bit more than half your towing capacity, you should never have a problem with it overheating.
Another possibility is your clutch fan. If you have never replaced it, it's toast by now. You wont believe how differently a new one will act.
I strongly recommend using only the expensive OEM part.
