I have a 99 cummins with 4.5in. lift. When I hit the gas i get a grinding sound in the front end, but when I put it in 4wd it stops. The fork assy. in the front axle that locks it in 4wd has vaccume pressure, but the ring started wearing down the end of the axle splines from a broken vaccume hose thats now fixed. Anyone have this problem?