Can they get a default judgement levy without trying to serve me and 3 mo later mail me a copy dated jan 11 th ,rec 4/13 called 4/1 made 50 payment and dropped off another 50 in drop box since they won't return my calls, they didn't even try to serve me a my old hb add my friends dads always there not once did anybody come to serve me , no letters nothing then reg mail to new add 3 mo later for a 600 balance left on a 2500 org due 50 mo 6 yrs I paid
What can I do to protect my car worth 3650. That all I own besides debt

Making payments does not stop a judgement, (it can be used as a defense if you had went to a hearing, if you are paying more than the late fees and interest are adding up to)

You can file in court to have the judgement over turned, but the judgement is valid, until you take them to court and have a judge over turn it.

So you will need to get an attorney and file to have it over turned on reason of invalid service. (although they can just serve you properly then and get another hearing. It will not stop a judgement merely delay action.

Also you only think there was not proper service. I do legal service every day, I tape a notice to the peoples door. (I take photo of street sign, house number and notice taped to door) That is all I need to do for the service I do here in Illinois. If that is the last known, or a address that they have on file, normally that is all that is needed.

They can get a default judgement. But you can fight it if you can prove non-service. However, that is only a delaying tactic. As you will be properly served before you leave the courthouse.