i have a 1994 S10 Blazer 4x4 w/ 4.3 Vortec, 4 door. I have had this truck for a while and have never had the 4wd working. When i put it into 4wd the transfer case locks in and the rear also locks with 4Lo. After any attempt to put it into 4wd it makes some odd noises, while driving down the road out of 4wd after such an atempt, the truck will start making a load howl, then a grinding noise as you slow, then at about 2 miles per hour, it makes a loud bang and it all stops. It does this for days and even once up to a month till i changed the cableand relieved pressure. Me and a friend put it on a lift and put it into 4wd and the front drive shaft rotates but meets no resistance. I have replaced the vaccum lines, the diaphram and the cable line to the front diff. My buddy suggested that i just go get a front end from the junk yard and do a swap. But i want to try and thing that can keep it cheaper. It was also mentioned to me that there is a fork inside the front diff that pulls the gears into 4wd. Is this true?and if so is that a buyable and driveway changable part. Any help is much appreciated.

 

It definitely sounds like things are not working properly in the front axle engagement mechanism. There is a fork that connects the passenger axle with the differential.

You can buy a kit that replaces the problematic vacuum actuator with a cable for quick, positive engagement of the front axle, but that would only work if everything inside the front axle is working properly. You can start by pulling on the cable yourself at the vacuum actuator, attempting to lock the front axle in.

 

ok....im gonna try to work on it today and see if i can get anything out of it. Its just driving me crazy and i need my 4wd for this winter. I will repost if i get anything new. Thanks

 

You can start by removing the three bolts where the cable attaches to the front diff. If you pull there, the front end should be engaged. To check, hold one wheel while spinning the other and the front driveshaft should turn.

 

i did what you said about taking the cable cover off the side of the diff on the front off my blazer and pulling it and trying to turn the drive shaft and it didn't turn. then i started my truck and put it in and out of 4wd and found what i think is a problem. my diaphram has constant vaccum so when it goes into 4wd it doesn't release the front diff when taken out of 4wd. Any suggestions?

 

If the actuator is getting constant vacuum, then the vacuum switch on the transfer case is most likely at fault.

But one thing is odd... You say that when you pulled on the cable to engage the front axle, held one tire while spinning the other, the driveshaft did not move?? Can you clarify? Was the transfer case in 4wd already? Did the tire you were attempting to rotate move at all?

 

sorry....when i did it the drive shaft did spin is what i meant...
but when i put the truck in 4wd the transfer case goes in fine....would that be if the unit on the case was bad?....also the vaccum line to the actuator come directly from the block...is that right?

 

If you were to follow the vacuum line from the actuator, it should go back to the transfer case. There is a small vacuum switch on the top of the transfer case which directs engine vacuum to the actuator when the transfer case is in 4wd mode.

 

ok....im gonna go check that now...so ill post and let you know...thanks

 

good news my friend, good news....ran to advanced auto and bought one of those switchs and put it in and everything works good so far.....now just trying to find some place to go test it out and see how good it works.....Thanks again Kyle....you have been more help than anyone has helping me figure this out.....i will post again after i get back to tell if all is absolutely good....