My trans has just started to slip when cold. Doesn't do it all the time. Only after it's sat overnght or a couple of days. Put it into gear and start to rev the gas and nothing then a couple of second pause and it drops into gear. May do it pulling up to a light-come to a stop, go to accelerate and a pause- drops into first and I'm off. This is always only within the first half a mile when cold. Once the cars all warmed up she runs fine- upshifts and downshifts fine no pauses or delays no slippage. Suggestions? 
