Yesterday I tried my 4x4 in my '03 ZR2, and it did not work. The roads were slick and I had to stop on a hill to wait for a HP. When I started to go I had no traction. I pushed the 4x4 button and still nothing. This is a vacuum system that pulls a cable to engage the front differential. The transfer case did engage. I did some research and the most common was the cable seizing.

My first diagnosis was to be sure I had vacuum to the actuator. When I looked under the truck my lines had dropped down onto the cat. I cut the bad section out and spliced them back together. The 4x4 works!!

It must have happened a while back because my heater wouldn't switch to floor. This switch had acted up years ago, so I was planning on repairing it again. However this vacuum leak was also causing this problem. There were no codes or noises (hissing, whistle) from the vacuum leak, so the computer compensated for it.

Good find! Nice when it's a cheap and easy fix..

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The actuator is located under the battery box. I almost started to remove items to get to the vacuum line, but then decided to check it from underneith. Plus this is outside in the snow since the Corvette is disassembled in the garage.

sweet!

ya ,, ya cant beat that wid n ugly chick can ya

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I rememeber this.. had one that was keeping the front diff locked..

2001 s10 crewcab - n musta got jinxed ,,on way home to lunch id hit 4x4 n dint switch right away ,,hit again then clicked in,,but then wouldnt click out ,,sosin were stuck in 4 h..no lo no 2h..looked fer vac lines ,,pulled n cleaned transfer case lectrics,,no good,,test of switch showed mod should be werkin since lights flashed when tunrt on key ,,but then pulled the pass. kick panel to find the (tccm)transfer case cab module ,,unplugged all looked clean n dry..squirted sum lectric cleaner on chit n put back tagetha,,wala werks as should now...like them fixes ,,that fuggan mod. is awmost 500 denaroos..purty commin issue in s10 period..