Just got my first blazer, everything is pretty awesome, loving it except for a few little quirks.

Anyway, my question. How does the 2wd system actually funtion? I have a 3 button console, and the zr2 package. How does the 4wd system engauge? When i press 4lo, i hear the parts moving and the system engauge. So im assuming a mechanical motor moved the Tcase in some way. I suppose this is how 4hi should work too (mine doesnt....). The part that confuses me is the vacuum actuator under the battery. What does this actually control?

if the tcase didnt shift, but the vacuum actuator did, what would happen?

If the actuator didnt work, but the tcase shifted, what would happen?

Ive looked though 15 pages here and 24 on the zr2forums now, but cant seem to find an answer. Also searched here but nothing is similiar to my symptoms.

The reason im trying to get an understanding of this is because (as previously mentioned) my 4hi doesnt work. I press the button in drive, and nothing happens. The 2hi just stays illuminated. I know the button works however, because if i put it into nuetral and press 4hi, both 4hi and 4lo blink a few times, and then it goes back to 2hi. I cant hear anything move or anything happen when i do this either, just a small click from the dash.

4lo works just fine however.

any insight would be greatly appreciated. I just disconnected the battery for the night, ill try it again when i wake up.

 

I just stumbled across this http://www.shop.synergyoffroad.com/p...5&productId=74 , maybe an answer to your probs? i dunno

 

I know I have gone through the description of how the system works before, but will repeat since it is easier than searching myself.

The transfer case has an electronic motor on it which turns the shift sector shaft to put the transfer case into each of the modes (2HI, 4HI, 4LO). For either of the 4wd modes, a switch on the top of the transfer case is activated (231 & 233 only - 246 has an electric vacuum switch). This switch controls vacuum to the front axle engagement actuator (shown in the link posed by amazinnblazin). This actuator pulls on a cable that pulls on a shift fork inside the front axle, pulling a collar to connect the passenger side output from the differential to the passenger side axle shaft.

Problems that you could have include a cut or cracked vacuum hose (very common), a faulty vacuum switch on the transfer case, a faulty vacuum actuator, a frozen cable, or a problem internal to the front axle (not very common, but does happen).

 

Wow thanks thats exactly what i was looking for! So the range selector (4hi 4lo 2hi) changes the gear ratio/transfer case setting, and the vacuum actuator engauges the front diff. Im out looking at vacuum hoses right now, hopefully i can get this fixed. now a very urgent thing right now, but it is annoying.

 

Well, its fixed. I press the button and it goes right into 4hi and sticks it. I checked all the vacuum lines and they looked old, but they wernt bad. I checked the actuator and it held pressure. I made sure the cable was free. I put it all together and it worked, i think it may have been to do with disconnecting the battery.

I tested it on a nice hill in my backyard, definantly works

Thanks again!