c4 lost third gear except under power

hey guys my c4 started acting up last weekend after i went to the track but it will not go into 3rd with out me manually shifting under hard power thats when its cold it shifts on its own when the tranny is warm but has alot of hesitation when shifting are there any ideas what it could be

 

Does the oil smell burnt, have you checked the vacum hose going down to the modulater on the trans, when you pull the hose off the modulater does any trans fluid drip out?

 

Ok not to but in but this happens to me too.mine smells like somethings burning

 

Check the modulator and the vacuum hose running to it.
If the fluid smells burnt, you probably burned the clutches. Rebuild time!

 

This will be the third time -_- I need a better build for all that power