Hey guys okay so both 4hi n lo wwork fine but just take forever to engage. Any ideas on what it could be and if it will cause bigger problems down the road. Thanks

 

on my 1992 full size blazer replacing the thermal actuator fixed this problem for me.

 

Really depends on what the OP is driving. The s-series trucks do not have a thermal actuator.

If it's an s-series, it is likely either a vacuum problem, or a problem with the cable running to the front axle from the vacuum actuator that is located under the battery (or on the fender for the older models).