99 blazer stuck in 4wd

My blazer is stuck in 4wd. The lights are working says its in 2 drive but the only way to get it back in 2 wd is unhook the vacuum switch. I push the 4hi button and it will go in 4wd but doesn't switch back to 2wd when I push the button. The acutator under the battery is working and we changed the switch on the firewall but nothing has worked. I have four button Auto 4wd 2wd 4hi 4lo.

Thanks

My blazer is stuck in 4wd. The lights are working says its in 2 drive but the only way to get it back in 2 wd is unhook the vacuum switch. I push the 4hi button and it will go in 4wd but doesn't switch back to 2wd when I push the button. The acutator under the battery is working and we changed the switch on the firewall but nothing has worked. I have four button Auto 4wd 2wd 4hi 4lo.

Thanks
How many miles on it and has transfer case ever been serviced with the GM blue transfer case fluid?
Have you tried backing up and rolling forward or putting it in neutral?

If the auto transfer case it needs to be put on a transmission /transfer case scanner and get codes and do shift test.

Post back any codes.

Mileage is 117,000 mileage and since we have owned it for about 6 yrs the transfer case fluid has not been serviced.

Mileage is 117,000 mileage and since we have owned it for about 6 yrs the transfer case fluid has not been serviced.
May or may not be your problem but it is.
If not serviced ever so often it will stir up many problems.
Long over due for service on transfer case fluid.
The transfer case fluid needs serviced with the GM blue transfer case fluid.