Ok ill start with the 1st 4x4 prob. Truck 1998 gmc jimmy 4x4 4door"3button", When i push the 4hi button it would act like it engaged in 4hi, But 4lo just flashed and would not engage Was just a vac. problem no line connected to the 4x4 act. under the battery tray, Plugged it back in and go everything was fine for the winter. Now 4 months later everything is acting normal push 4hi the light comes on, throw it in N and hit 4lo goes right in.....the f/driveshaft locks when you engage the 4x4 then spins free in 2wd, The gear reduction in 4lo is there, The click is there, but no power to the front wheels. I am not sure what the problem is. Anyone have any idea?

 

Your front axle isn't engaging properly. Check out the 4wd No Worky thread in the Tech Article (DIY) section.

 

I finally got around to checking for a problem, My 4x4 actuator boot was ripped in half. I got a new actuator for $40.00, Now my 4wheels is good as new, Thanks for the article.

 

Thanks for the follow up and glad you got your problem fixed so easily and cheaply!!