i cant get my front differential to lock in i put the car on the lift jacked off the ground and when i put it in 4wd a grinding noise like the front diff isnt fully locking in but i can unhook the cable of the front diff and pull the shaft with channel locks it will go but i have to pull pretty hard i checked my vaccumm and it had 22 pounds so i was wondering if it was the front diff and the easiest and cheapest way to fix it

 

It could be something inside the front diff. The only way to tell for sure is to pull the passenger side axle extension housing off.