1994 e320 transmission slippage

[calvertg]

My e320 transmission started slipping when in drive from a stop. If I put it into 2nd gear it goes with no problem I checked the fluid level and it was a quart low so I added up to the mark but still have the same problem. The fluid doesn't look burnt and it makes no funny noises. Should I do a service on the tranny or is this transmission toast? Thanks for any advice.