2nd Gen Non-Engine/Transmission 4wd suddenly went out, trucks stuck!

[VolsFan]

Ok, working local so attempted to take my wife into work. Roads are very bad. Had it in four wheel drive of course, then made it down to the main road and determined should just go back home. While going back up the hill, there was a noise at the front axle and all of a sudden I'm in 2wd. What gives? Gonna get pulled out once roads are better hopefully today, the truck is sitting on the side of the road. Any ideas what I'm in for?

 

[KRStone]

You wrote the vehicle went back to 2x4. What do you mean? Did the light turn off or did the front wheels stop spinning? What kind of noise? Noise was one time or did it keep making noise when you tried to drive it?

Need to determine if it was front driveshaft, front differential, or a front axle, or a drive axle ujoint, or a hub.

 

[VolsFan]

My 4wd light hasn't been working properly for a little while but 4wd has been engaging fine. Was going to get a new sensor for it today. So there was no light on when I was in 4wd. Going up a steep hill in 4wd there was a single clunk noise and then my front tires stopped turning and back tires started spinning. Had to back it up and off the road so the plow trucks could get through.

 

[MLee]

Did you attempt to re-engage the front axle? chances are that it wasn't fully engaged to begin with and it slipped out of engagement.

 

[MrWill12]

I have a manual 4x4 transfer case lever and I sometimes I have to pull back on the lever, firmly, a second time to engage the 4wd, but I don't recall any noise coming from the front-end.

On a separate note my 4wd failed to engage because the vacuum tubes connecting to the actuator had been chewed through, compliments of a mouse no doubt.

 

[DonFitzwater]

Just had a similar occurrence on a 94, turned out to be a plethora of problems that were solved with a vacuum harness, shift motor, fork and pads as well as an axle shaft (popped loud and sheared at the end of the splined area at the diff)

 

[Road Dog]

Mine would pop out of 4WD but adjusting the transfer case linkage fixed it. Or it could be the CAD or the vacuum lines to it or the vacuum switch in the transfer case.

 

[VolsFan]

Thanks for the replies. One thing I know I can rule out is vacuum. My lines are in perfect shape. Got my dad to pull me out, had to back it out on the main road and drove it down to a park and ride til the road melts enough to get up in 2wd. It is definitely not engaging. Going to have to farm it out, hoping for the best, if it's not one thing it's another with this thing lately

 

[SnoKing]

Sounds like worn fork in the CAD system, and that is why you were not getting the 4x4 light. Hopefully you did not break anything else. Here are a couple youtubes. Chris

http://www.youtube.com/watch?v=i-gHnwnzfmI

http://www.youtube.com/watch?v=SgI1tdS98Gk

 

[VolsFan]

Thanks for all the good info. It did end up being the actuator. Ordered the posi lock kit so this doesn't happen again, was going to put another vacuum actuator back on but figured I don't need 4wd too much for the next few days so wanted to get a more permanent fix.Fork looked ok. Looking forward to this mod

 

[SnoKing]

Good job! Chris

 

[JMcCoy]

Glad to hear you figured it out. The vacuum cad is junk. The Posi-loc works good. Not as good as a solid axle, but good. Just remember, when you are shifting in or out of gear, always operate the transfer case first then the Posi-loc. You can even shift into 4wdh at speed, just like stock. A common mistake people make is they try to engage the Posi-loc first, but it will just grind. Good luck

 

[CM_Guest]

Your lines may be in good shape but what about the pump? They can wear out. It's also possible you had moisture freeze in your vacuum lines. The easiest way to spot vacuum or vaccum pump issues is by how the heater and air conditioner work. If the air doesn't come out of where the mode knob is pointing you probably have a vacuum issue. It's also possible you snapped the axle disconnect sleeve that connects the two shafts when you put it into 4wd.

 

[SnoKing]

Your lines may be in good shape but what about the pump? They can wear out. It's also possible you had moisture freeze in your vacuum lines. The easiest way to spot vacuum or vaccum pump issues is by how the heater and air conditioner work. If the air doesn't come out of where the mode knob is pointing you probably have a vacuum issue. It's also possible you snapped the axle disconnect sleeve that connects the two shafts when you put it into 4wd.

Read OP's solution in post number 10. It was the CAD vacuum motor. Chris