4x4 not engaging, 1990 1500
 

Hey everyone, I've got a 1990 chev, reg cab long box auto 4x4, I just put a new rear main in and after putting it back together the 4x4 is not engaging at the front axel, the transfer case engages but as far as I can tell the front end isn't locking, I havn't had the chance to put it in the air to check it out yet, hopefully tomorrow I can do some further investigating, It looked like all of the plugs were connecting but I need to double check all that, before I did the rear main the 4x4 worked fine, it did want to lag a little on engagement, I.E. it took a second to fully enagage or you might have to shift it from reverse to forward to get it to click, but I've seen that quite a bit on these older trucks. Any info?
I'mnot totally sure how the front end works as far as locking, a friend of mine was telling me about a kit that locks the front end all the time then when you engaged the transfer case there wasn't any lag time, just looking for some ideas, info,and maybe a better understanding of what I'm dealing with here.
BTW if it matters its a 305 and a 700R4. Thanks for looking, any info is appreciated.

actuator has likely gone south, very commom problem with these trucks.

Wow, that was fast
how expensive/easily replaced is it? I was looking through a haynes but cant find anything about it

Very easy to replace, about $100 with a new wiring harness when I did one a couple years ago. It is a piece that threads into your front differential that engages when 4x4 is selected.

is the front driveshaft not spinning? or is the fronst shaft spinning and its not locking at the wheels?

oh to find that out....jack all four tires off the ground and see what spins and what doesnt when ya put it in 4