My 99 Tahoe has the NP8 option "auto 4wd" and my frts aren't digging I have it up on stands and the frt d-shaft spins when engaged but no power to the frt wheels. This leads me to believe it is the frt actuator mtr chevy so commonly had problems with it has a 4 pin connector can someone tell me how I can test it which leads should have pwr on the connector? thanks

I cant remember the exact name for it, but you can simply pull it out, leaving it hooked up, switch it into 4wd and try and push it back in with your hand to see if it works. Another thing to tell you if it works is it will get hot.

Just one thing im curious though, Autotrac, its in 2wd until it senese slippage, then it applies power to the front, so if you have it on jackstands, and no tires are slipping, it would have no reason to engage 4wd. Of course it also matters if, when it slips, it engages the front wheels at the diff or the t case, that I am not sure of.

It can be locked in auto trac and 4hi-4lo or 2wd. I was pushing the 4hi btn I took the actuator out of the frt diff and pushed the button andnothing happened I wanted to know what lead to throw the test light on to chechk for power. I just replaced it with a used actuator I had in the yard and it works fine I geuss I got lucky.