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4 wheel not working
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Posted by: 84camaro_z28

i dont know that much about 4 wheel drive but i just bought a 91 gmc jimmy for real cheap and its a damn good SUV but i feels like the 4 wheel drive doesn't work all the time. the front drive shaft spins but the front tires dont spin. i completly jack it up to discover this. any ideas?

Posted by: cswrench

You have one of theese problems. There is a vacuum switch on top of the t-case that engauges the front diff. Theese vacuum switches go bad often, also the vacuum lines like to break. The vacuum lines one from engine one to front diff actuator the other to a sensor or is a dump valve. The front diff servo/actuator diaphram may be ruptured (unlikely but does happen) or the cable is siezed. Good Luck!!

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