i have a 97 blazer, bought it last year and put a 99 trans in and used the original transfer case that was already on the truck. 4 wheel drive gave me some issuses when I put the transmission in but i worked all the bugs out. everything worked properly. this year i went to use to 4x4 the other night and i can't get the front end to lock. put all 4 wheels off the ground and ive got both driveshafts spinning. took the battery and battery tray out and the accuator is pulling the cable tight. all vaccume lines appear to be fine, hvac works just fine and the accuator is pulling hard. I don't have any 4x4 lights flashing, and 4h and 4L are engaging fine, just the front end wont lock. any ideas? possibly my worst nightmare, front axel bad????

 

did you manually pull that actuator to see if the front end would engage. i had a 83, luckily they mounted them on the fender back then and it would only pull it like halfway. i actually had to put the truck in neutral pull it and roll the truck a hair to get it to lock in

 

no, but i will try. i took the cable end out of the actuator and hit the 4x4 button to see if the actuator was pulling hard enough, and it sucked itself flat. so im "guessing" its pulling hard enough. I hooked the cable back up to the actuator, put it back in 4x4 and went to the front axle. i took the 3 bolts out that hook the cable up to the axle and pulled on the cable. i couldn't get it to budge with it in 4x4 because of the actuator pulling all of the slack out of the cable. but this afternoon i will try your trick to see if i can get it to lock in.

 

It doesn't take a lot of vacuum pressure to pull the actuator flat with no load on it... Is the cable actually being pulled by the actuator? It needs to move 0.5" to 0.75" for the front axle to engage.

 

its moving at least that much and more probally. i had a friend of mine engage and disengage it several times to make sure its functioning. i found a bad spot on the cable over the summer and replaced the cable. like the insulation was rubbed down raw so i replaced it and never really check the 4x4 after replacing it. i know it is hooked up to the front axle and the actuator properly. ive double checked that, and when i engage it the cable is moving around like the actual cable is moving inside the insulation, cause i can see the cable end moving in and out of the actuator.

To abig84 i still haven't tried your trick yet but i need brakes also, so tomorrow is that day i will do all of this.

 

If the cable is moving and pulling on the shift fork inside the front axle and still the front axle is not engaging, then you may have a broken shift fork or collar inside the front axle.

This picture shows the shift fork and collar which are located inside the passenger side extension tube:

 

ok, new brakes went on without a problem and i turned my attention to the 4x4. double checked the vacume line and one of the seems odd. everything is working like it should, HVAC, actuator, and tcm all is function like it should. the top will nipple on the transfer case has a vacume line the goes into a tee. it is connected to the top and runs up to the engine, but the other piece is not connected. i pulled a vacume diagram off this site and im stumped. the loose vacume line has nowhere to be hooked up. all 3 little lines that come off the vac module are all connected, and looked to head up front to the engine. also i found a vac line near the brake booster that was unhooked. pictures would most def help if any of you have some of where that vac line goes into the brake booster and why is vacume lines hooked up weird on the transfer case, and the 4x4 did work? also, i newbe is asking alot, but it it possible for the shift fork, and collar to be ok and the "diffrential" where the front drive shaft goes into be bad???? i also wanted to add i checked to the if the shift fork was good. with the truck off, pushed the actuator in and felt it lock by pushing the vehicle back just a tad. and still no 4wd. thanks for the help

 

The "magic End" goes into a vacuum canister most likely. This canister is either located in the fender wall which is mounted in the drivers side fender near the break booster, or if it's an earlier 2nd Gen, it is a ball located on the good on the drivers side.

 

well, i finally got tired of tinkering and going over and over it again and, called a friend of mine who works at a local shop. we put it on the rack and went over it top to bottom and we both have determined that the front carrier shaft is bad. The front axle is engaging but there is no spin likely due to a broken ring or pinion im guessing. so I went out and bought a used front axle assembly today and will prob have it put in tonight.