93 Spirit Transaxle

This one has me puzzled, While cold, it will go into any gear just fine, once it warms up it loses forward gears. Reverse will still work though. Shut it off for just a few seconds, prestow you have forward gears again.. just not for long. Anyone have an idea as to mechanical prob or electronic?

Cheers

take it to a shop and have them pull up any codes stored in the Transmission Control Module's memory. When was the last time you had a transmission tune-up, fluid & filter change? When you did have it serviced, what type of fluid are you running in there?