I want to know what tranny is in my monte, can you tell from the vin#

it has the 3.8 liter engine but also has the two different tranny codes but i dont know which one, also says that only 2000 montye will fit, the one that is in there slips out of gear at about 35mph, is it fixable

most likey an internal failure. get a trans shop to confirm and give you a bid for an overhaul. usually runs around 1800-2200 Roy