after the engine warms and have driven a couple of miles,at the first
traffic light the trans bangs and then is stuck in 2nd.at first i thought had gotten rear-ended.I cannot shift it manually,fluid is up but it is due for a change.this trans was new installed in '99,4spd OD.when the engine cools off it is ok,but i get maybe 5 minutes and then its stuck in 2nd.any thoughts?

Unfortunately the trans is experiencing a problem that will require a tech to diagnose. It is going into the limp mode and when you shut it off for a while the computer resets everything. Take it to a transmission shop.