I'm banging my head against the wall and hoping someone can help. I purchased a 96 4.3l 4wd pickup in decent condition, but the 4wd isn't working. I'll list the things I've tried as I've narrowed it down significantly.
- The transfer case shifts in and out fine. When engaged, the front drive shaft spins as expected.
- I replaced the vacuum switch on the transfer case, which seemed to be stuck.
- Replaced a corroded vacuum line from the reservoir to the vacuum switch.
- The actuator under the battery actuates as expected when I connect a vacuum pump to the hose running from the vacuum switch.
- When using vehicle vacuum, the actuator moves about 1/4", not enough to engage.
- When I place the vacuum pump on the hose running to the vacuum switch, the actuator moves the same 1/4".
- When actuated, the hub locks and engages with the front drive shaft.