Quadratrac not engaging

[somedude922]

79 GM Turbo 400 , QT 1339, converted to part time. 4wd will not engage. I have vacuum at the switch, I can hear it when the switch is turned. When I pull the vacuum lines on the diaphragm, I have vacuum coming from the diaphragm on the t case. Am I supposed to have vacuum coming from the Transfer Case ? There are no vacuum leaks that I can see.


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[Posi]

You say there is vacuum at the diaphragm, it should then pull the linkage. Is the linkage moving?

 

[somedude922]

Im not sure how I would know if it is. Isn’t it inside the case?I am assuming it is not though.


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[Posi]

Does the rod behind the diaphragm move in (towards the diaphragm) while you apply vacuum?
The rod should move when vacuum is applied if it doesn't the diaphragm could be bad. When was the last time the Transfer Case was in 4wdr?

I'm going off a wagon Q-trac I worked on a while back and assuming the CJ unit is the same.

 

[somedude922]

I will check tonight. Last time in 4wd was 3 months ago.


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[Posi]

Make sure you check vacuum on the apply side of diaphragm (nipple closest to Transfer Case ) with engine running.
If you find vacuum turn off engine
With the engine off pump up the vacuum to 10"
You should hear a click of engagement
If you don't hear the click your diaphragm is toast
You can find them on ebay, their not cheap
If you do hear a click check all your vacuum hoses.

Hope this helps.