2000 blazer
3 button switch

loud bang when engaged in 4hi seems to slow the truck down considerably, only way to take out of 4 hi is to go in reverse, drive shaft from the transfer case to the front differential seemed to bash a hole in the bell housing where the universal joint is. i removed the transfer case vacuum switch and cleaned it to check for sticking, filled up the front differential which was low on gear oil.... still is screwed up. checked the vacuum actuator, it squats down when in 4hi and seems to be doing its job. big headache. if it needs professional work how much would it cost! thanks forum!

 

PROBLEM fixed mismatched front tires.....sounds stupid but the spare was a little smaller and i didn't notice till i got close and read the numbers.