How far behind on an auto payment before repo usually?

1-45 days.........................................

It depends on the individual creditor; the value of the vehicle and the amount of debt. Some will repo within days and others might take several months. But don't fool yourself. If your car is repossessed that doesn't get you out of paying for it. They will auction it for whatever they can get and you will still owe the difference between that amount and what you owe; plus late payment fees; repossession; storage; transport and auction fees; plus legal fees and document fees plus whatever other penalties are specified in your purchase or lease contract. All told it could add up to thousands.

It varies widely. Some companies will repo after one day late with one payment; some will work with you.