Alright so heres my problem. I hit the 4 wheel drive button. It lights up and enguages. I go underneath and the half shaft locks. So I know its not the switch or the transfer case. The front wheels wont enguage though. Ive replaced the item under the battery box and traced all the vacum lines. Any thoughts.
thanks, Brian

 

Is the actuator under the battery receiving vacuum when in 4wd, engine running? If not, the problem lies either in the vacuum lines or in the vacuum switch on the transfer case. If it does and it pulls the cable the required 1/2" or so, then there is a problem in the front diff. Both of which have been covered extensively in other threads.

 

every s10 ive owned had this problem. my 83 and 85 the actuator was on the fenderwall so i would manually pull it and use vice grips to hold it in place.

 

Very common issues for sure.

 

it pulls but i dont think it fully enguages and i cant find a leak. you dont think its that sensor on top of the transfer case do you?
thanks anyways fellas.

 

If you help pull on the cable with a pair of vice grips, can you get it to engage? Have you put a vacuum gauge on the supply line to verify that it is full engine vacuum indicating that there is not a leak?

 

no I havent. not sure where the supply line is.

 

By supply line, I mean the line that connects to the actuator. It is what supplies vacuum to the actuator. If you hook a vacuum gauge here and take a reading with the engine running, transfer case in 4wd. Then connect the gauge to a direct engine vacuum port and compare the readings.