front differential

[willybobba]

I know most of you all have AWD front differential's, but for the time being I have a 1989 blazer with 4wd. I've had good luck so far posting in here when I have problems. the problem I have is that it wont shift into 4wd. I have vaccum, and the cable is not broken. I have taken all that apart to find nothing. the light does not come on on the shift quadrant which would tell me that the cable is not being pulled far enough, however I couldn't get it to pull far enough just pulling on it myself. the 4wd does not engage while I am pulling on it eaither. This tells me it is somthing inside of the differential, but before I go ripping and tearing I wanted to see if anybody has any ideas what it could be. 4wd worked a week ago, 2 days later it didn't.

 

[Crazy J]

what do you mean by you have vacuum? do you have vacuum coming from the switch on the t-case? or do you have vacuum going to the switch?

if you have vacuum coming from the switch then check your lines for leaks and check the actuator for leaks or tears. if that checks out then the problem is internal and the diff will have to be pulled.

hopefully it's just the vacuum switch, it's only $20 and easy to reach.

 

[willybobba]

everything is fine up till the differential it is somthing in the differential and I was wondering if anybody knew what it might be or what I might look for before I tear into it and put the vehicle out of commission

 

[Crazy J]

i'm of no help, i suggest you try asking this at s-seriesforum.com or s-series.org

 

[jwaller]

the 4x4 front diff has a vac actuator on the pass side front axle. try making sure your getting a good vacume signal there when you shift into 4wd. most times it can be traced to old rotten vac lines.

I suggest you put a manuel cable on there and ditch the vac system. summit and jegs sell them for about $100. it's nice to have 4wd low and not have the front pulling. so you can drive on pavement without the hassel of it binding up the truck.

 

[willybobba]

this particular year has the cable that runs from the front diff to the vac acctuator under the battery tray. everything there works fine I have already had that all apart, this is why I know it is inside the differential. I can't pull out the pin far enough to make the fork engage, or even turn the light on in the shift consol.

 

[Crazy J]

have you tried jacking up a front tire, spinning the tire then pulling the cable?
usually you can't engage the front axle but just pulling the cable, the tires need to be turning at least a little bit.

i still think it's vacuum related, i've owned several 4x4 s-10's and blazers with varying mileage and have never had a problem with the front axle itself, always with the vacuum.

if my tip doesn't work then you'll need to pull the diff and check out the passenger side axle, either the shift fork is stuck or something is worn out.

 

[willybobba]

I am thinking that I am gonna have to pull the front diff. I have already jacked up the front end and completely removed the cable, then spun both the drive line and a tire or two and no motion, while pulling the actual pin itself. I know all the vacumm stuff is working cause I can shift into it and it all works correctly. the for just wont go into its slot.

 

[Crazy J]

where in WA you located? im also in WA and can send you parts if you need some.

 

[ItsMyTy]

i've had one where a thrust washer was so worn it broke, in the shift fork area and caused just a little bit more clearance and the engagment ring wouldn't move enough to lock in the right side axle.

you can take the right side axle tube out and see what's going on without taking the whole differential assembly out