98 Blazer 4HI not working

[blazerman47]

Have a 98 Blazer. Last fall had the trans replaced and lost all 4 wheel drive ability during worst winter on record. Got 4LO working, but having trouble with 4HI . I can hear clicking underside but not full engagement. I looked at vacuum lines at the air actuator and found it pulled off, and the T hose on driver side are new. The hose is not the tightest. It can be pulled off with little effort. I took the tccm out but it look fine. I'm at a loss and need help.

[blazerman47]

Update: found vacuum line cut. Replaced line, transfer cas switch, new 4wd actuator and still no 4hi. Vacuum is not pulling cable at actuator. Drive shaft locks , but no 4x4. Buttons on dash can be put into 4lo when vehicle in neutral. 4hi light goes on and off. You can hear clicking underside of truck when the buttons are switched. Need help!

[Blue Bowtie]

If the front driveshaft locks in, the transfer case, its controls, and the TCCM are O.K. Make sure the actuator under the battery tray is getting full vacuum and can move the lock pin in the front differential.

You should be able to manually compress the vacuum actuator and move the cable, and thus the differential lock pin. If the cable is damaged the system won't work. If vacuum is inadequate, the system won't work.