My nephew's probe over drive light blinks. When you first start it up (cold) it would not shift into dive. Then on the second start the light started blinking and it would shift into drive.

Only thing I can think of is a vacuum leak. Any suggestions????

Most likely he is looking at having the transmission rebuilt or replaced. When the O/D light flashes it is like the CEL (Check Engine Light) coming on, only for the tranny. This is an alarm to let you know that there is a malfunction in the transmission. I would suggest making a trip to Autozone to have them pull the codes form the car. They do this for free. If you don't have an Autozone nearby then you can pull the codes yourself by taking a small piece of wire or a paperclip and jumping the TAT and GND pins in the diagnostic connector. Turn the key to the acc position and watch the O/D light for flashes. A long flash equates to a 10, and a short flash equals a 1. For example, five long flashes followed by five short flashes would be code 55 which is the Vehicle Speed Pulse Generator.