overdive slipping 1998 i30

[thegman]

the transmission seems to slip in and out of gear. It works ok with overdrive switch off. when you accelerate hard the rpm's goes to max but transmission not engaged, until you throttle back. Even at lower speeds it seems to engage and disengage. Also I can hear a faint chirp as it engages and disengages.

I am looking for directions for troubleshooting

The fluid is slightly brown but not burnt

Thanks for your input