i got 98 s 420 transmision was rebilt b4 45 days i soon the car rich the 80 f temperatur the transmision got problem dont shift good i D but if i go in 4 work good down shift ap shift ok in D dont wona work i down shift

i think i disected that and understood

If its been rebuilt by a mechanic take it back to him!!

oh man this is painful.
Anyway, start with the basics. Check tranny oil, change filter and go from there.
good luck