when ever my engine is running my front axle is always locked in, when i shut the engine down it takes about 15 mins for the vacuum to bleed off and the actuator disengages and i can spin the front drive shaft like normal. what could cause this and will it cause me any problems when i put the truck on the road. and it didnt always do this, it just started out of the blue one day

 

What 4wd system do you have; 3-button switch or 4-button switch on the dash?

If 3-button, it could be a faulty switch on the transfer case or it could be improperly routed vacuum lines.

If 4-button, it could be a failed vacuum solenoid on the firewall or (again) improperly routed vacuum lines.

 

i have the 3 button system (98 4dr LS), when i bought it had a fualty TCCM. i replaced that and everything worked fine. i was playing around with it shifting in and out of 2hi, 4hi , and 4lo. i had chacked everything over several times and one time i crawled under and the drive shaft would not turn in 2wd. i jack up a front tire and relised the vacuum actuator was still engaged. its been like that ever sence, i think the vacuum switch on the tcase is stuck in 4wd posison.

i never touched the vacuum lines, it worked and now it dont work right idk why exaclty

 

Sounds like the vacuum switch has failed in the open position. If the lines are proper, that is the only thing that could cause your symptoms.

 

well i can still use 4wd and 2wd just fine, i was mainly concerned if this will give me any problems down the road

 

If the front axle is fully engaged, you shouldn't have any problems other than a decrease in fuel mileage.

 

how much of a decease are we talkin 1mpg every bit counts

 

what is that switch called and is it a dealer item only? I assume we are talking about the one on the front axle?

 

The vacuum switch is located on top of the left side of the T-case. When the fork moves forward when you put it in 4 wheel drive it opens up to port vacuum to the front drive axle actuator. I'll stop there. Every time I think about how the 4X4 system works in these things it just drives me up the wall. Can anyone say "Rube Goldburg"? Can't actually believe someone would put a system like that in a production vehicle. But don't get me wrong. I love these damn things.