Hey I've got a 97 S-10 Blazer with 4 wheel drive issues: When I try to put the vehicle into 4 hi or lo the indicator light on the dash is showing that it went into 4x4 successfully, I can also FEEL the transfer case engage and shift in.... BUT, the front differential is not engaging.

I've checked the vacuum actuator beneath the battery tray and it is not engaging and pulling on the shift cable. I've disconnected the vacuum line from the actuator and I do have vacuum pressure to the actuator. How much suction is needed to engage the actuator and pull the shift cable? I am getting vacuum suction constantly whether the vehicle is in 2 4hi or 4lo, and it seems to be about the same amount of suction for all (Not very much).

Is the vacuum pressure to the actuator controlled by the vacuum switch located on the transfer case? Am I supposed to be getting suction at the actuator even when the vehicle is in 2wd?

Lastly, I've come across mention of a vacuum switch that is line from the vacuum resevoir to the actuator beneath the battery tray. It is supposedly by the firewall somewhere near the distributor? Could this be my problem? I recently replaced the cap and rotor and may have bumped something loose and not realized it?

 

You should have close to the same amount of vacuum as what is available at the engine.

Yes, the vacuum to the actuator is controlled by the vacuum switch located on the transfer case. No, you are not supposed to be getting vacuum to the actuator when in 2HI.

The electronic vacuum solenoid is only used on the 98+ NV236 (Auto4wd 4-button transfer case) so you don't have to worry about that.

 

Thanks, I found a vacuum leak right by the reservoir which may be adding to the problem but I'm thinking my problem is more with the switch on the transfer case.