My 4x4 won't engage on my 94 blazer.

the light goes on and the transfer case engages and i checked the diaphragm under the battery box and it seems to hold pressure.
now i have vacuum but to me it seems a little weak so i think that might be the problem. anyone know how much pressure there is supposed to be?
any help is appreciated , it could snow anytime now

 

Should be somewhere close to engine manifold vacuum pressure. If it is low, then you have a cracked line somewhere.

It is also possible that the cable itself has started to freeze up a bit. You may need to lubricate it.

 

Shoot man, just change out that crappy vacuum actuator for a locking cable.

Here is my how-to Very simple to do and only $25

 

Just finished troubleshooting my own 4WD-won't-engage issue. I just replaced the vacuum valve that hangs in the bracket near the firewall $54 + tax. I was in a rush, needed it done. If the actuator itself ends up failing, I'm going to go with a cable lock myself. I wish I'd had time to go posi-lock cable in the first place, but it just wasn't in the cards.

 

Hey, ya do what you have to do.

I would consider it whenever you can to go with the cable system. That way, when it gets really cold or really hot out, you know it's gonna lock no matter what.

 

With Auto4wd, going to a posi-lock setup will cause issues with your TCCM.

 

crappy, really? even if I don't use auto4wd?

 

If you do not use it, you may not have any issues... It all depends on when you use 4wd. You should be fine, but the TCCM in an Auto4wd truck monitors the front axle engagement (via the trigger switch in the front axle) for proper engagement. I am not sure if it monitors it for disengagement. You may have to get a routine down for engaging and disengaging the front axle whenever you use 4wd.

 

good to know, thanks Kyle.

 

Good info.

So then, what years or models have the Auto-4WD?