Once I turn on 4WD, a few seconds later it slips back into 2WD. To bypass this I permantly attached something to keep the actuator rod extended. What would be causing this to loose the vacuum to deactivate the 4WD. I thought it had a leak but never found one. Ideas?

 

Bad switch, bad actuator, partially frozen cable, or a vacuum line problem. What have you done to try to cure the problem?

 

All I have done so far is clamped a pair of vice grips on the cable at the actuator so the cable will stay engaged at all times (god forbid I need 4WD in an emergency). I just think it's not the right thing and it also constantly keeps the front gears (4WD) always spinning. - engaged, I think, can't help the gas mileage either.

 

fF it works and then slips out, but works when you have the cable vice-gripped, its probably a problem with the vacuum actuator or lines. It might have a small hole that allows vacuum to initially engauge the system, but then slowly bleed it off.

I think i read somewhere someone having the same problem, and this was it.

 

Yeah, I would start with replacing the vacuum lines to/from the vacuum switch.

If you had a vacuum gauge, you could compare the vacuum pressure at the intake manifold with the pressure at the actuator when in 4wd. If they are not very similar, then you have a leak.