new blazer, need HELP with 4x4 system

[Nate17170]

Hello all, I just bought a 91 blazer 2dr, auto, 4.3, 4x4, all options, 145k. $1500. Its rolling on new Yokohama Geolander tires, and is in great shape. I am happy with the deal I got.


BUT... the four wheel drive system is not working properly. From what I read from internet searches and general knowledge, it seems to be the vacuum actuator system failing. First, I was able to put it in 4x4 Hi and Lo, but the light up drivetrain did not light up at all, and I also had no 4x4. So I read around a little bit, and eventually ripped out the battery and tray to take a peek at the actuator. I played with it, worked it a few times by hand, and sprayed some silicone lube all over it, and the shaft that pulls the cable (it all seemed pretty rough, but still it went in and out. After I put the battery back in and started it up, the light up drivetrain was lit up. But it was only in 2wd. I checked 4x4 Hi and Lo, both worked flawlessly. But even after "testing" the four wheel drive system (which got me in and out of a rough local trail VERY easily), when I put it back in 2wd, the drivetrain light stayed on. After a while, the light went off, and BAM! No more 4x4 at all. The front driveshaft turns fine. But the front wheels will not spin.


I was thinking about putting a posi-lock on it. But I can't think of a reason that it would have worked like that, then just shut off.

Any suggestions, or advice, would be greatly appreciated.


Thanks, Nate

[rlith]

Quote: Originally Posted by Nate17170

Hello all, I just bought a 91 blazer 2dr, auto, 4.3, 4x4, all options, 145k. $1500. Its rolling on new Yokohama Geolander tires, and is in great shape. I am happy with the deal I got.


BUT... the four wheel drive system is not working properly. From what I read from internet searches and general knowledge, it seems to be the vacuum actuator system failing. First, I was able to put it in 4x4 Hi and Lo, but the light up drivetrain did not light up at all, and I also had no 4x4. So I read around a little bit, and eventually ripped out the battery and tray to take a peek at the actuator. I played with it, worked it a few times by hand, and sprayed some silicone lube all over it, and the shaft that pulls the cable (it all seemed pretty rough, but still it went in and out. After I put the battery back in and started it up, the light up drivetrain was lit up. But it was only in 2wd. I checked 4x4 Hi and Lo, both worked flawlessly. But even after "testing" the four wheel drive system (which got me in and out of a rough local trail VERY easily), when I put it back in 2wd, the drivetrain light stayed on. After a while, the light went off, and BAM! No more 4x4 at all. The front driveshaft turns fine. But the front wheels will not spin.


I was thinking about putting a posi-lock on it. But I can't think of a reason that it would have worked like that, then just shut off.

Any suggestions, or advice, would be greatly appreciated.


Thanks, Nate

Did you check if any part of the actuator was leaking?


1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor

[mortgageman1484]

Quote: Originally Posted by rlith

Did you check if any part of the actuator was leaking?


1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor

I have a 94 4dr 4x4 with the exact same problem! There are two switches on the dash, left of the steering wheel to engage the 4wd and to shift from hi/lo. I'm in the process of replacing a radiator and have the battery and tray already out. I put the vaccum actuator on a vac pump and it tests fine. The vaccum hoses are mostly dry rotted and I intend to replace all the hoses. I'm not seeing any hoses to the transfer case. What size are they and where do they connect?

[rlith]

should be 7/32, and they connect to the vac switch on top of the transfer case.

[Nate17170]

I put a posi-lok kit in mine. 4x4 works, but man, what a pain in the ass to get it to engage. I wish I would have just replaced the vacuum actuator for simple 4x4. And for $100, they should have had a better manual. All that is in the kit are a few screws, two simple mounting brackets, and the cable. Just to be nice they threw in some zip-ties.


BOOOOOOOO posi-lok.

[mortgageman1484]

How about a vacuum hose diagram! Is there an online source to download and print a complete and accurate diagram? The previous owners of my truck have done some hacking. I've found two hoses not even connected to anything. Maybe that explains some idle and driveability issues. I'd love to have a correct diagram to make sure I've go the correct hose routing.

[rlith]

Quote: Originally Posted by mortgageman1484

How about a vacuum hose diagram! Is there an online source to download and print a complete and accurate diagram? The previous owners of my truck have done some hacking. I've found two hoses not even connected to anything. Maybe that explains some idle and driveability issues. I'd love to have a correct diagram to make sure I've go the correct hose routing.

www.alldata.com