My atomatic runner does not engage in 4wd when i try to drop it into geer. I replaced my cv joints yeterday, when the job was done i took it up a trail and also ran over a log. Has replacing my cv joints, or runing over that log, might of been the cause of knoking somthing loose, or what else might it be; Where do i start??? I can hear a click under the dash.....and when driving 20mphh I can feel a slight rev in the moter when shifted....but now power to front tires and no 4wd light

 

just bought it and want to learn to diagnose this stuff my self but need some help

 

an expert should chime in but does your truck have ADD or manual hubs?

If its ADD, then it could be that a vacuum pipe is loose or something. and wire to the ADD actuator.

 

auto locking hubs

 

where is the wire to the add acuator??......is it on the front diff.....next to the two vacume lines?.....and the vacume canister under the front right side do I have to take it off to see the hose on the other side??? or is there only one hose

 

can anyone answer my questions...I would be really gratefull

 

Vacuum engages the ADD; there's a connector that runs down under the distributor, by the oil pressure sending unit (if 3VZE) & connects to the diff for the light in the dash. Check those. There are TWO vacuum hoses running to the front diff that actuate the ADD.

 

disconnect the vac hose to the dif and run a seperate vac line straight to the diff from a vac scource on the intake, one port at a time, that will bypass solenoids and force the axle to engage. then just put it all back and it should function properly, thats all it took for mine.

 

Check all the vacuum hoses - I had this same issue at the end of last winter after replacing 1/2 of all my hoses. I discovered a hose completely disconnected from an actuator. No biggie - just had to plug it back in and it easily engaged again.

Most of the hoses and valves/actuators are on the passenger side of the engine behind the battery, just above the wheel hub. It's a pain the ass to check it all, but you'll get the idea.

Diagram example:

https://www.yotatech.com/attachments...ence-vac-2.jpg

Also, check near your front differential. There are 2 different hoses that plug into the front diff. If those are disconnected you could also be having the same issue.

Best of luck.

Ben