Won't engage in 4x4
09-25-2009, 09:27 AM
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I had the exact same problem like 3 weeks ago. It ended up being the ADD vacuum diaphragm that switched the little sleeve onto the shaft inside the axle tube. Its VERY simple to fix.
1. Unbolt the ADD modulator on the front of the front diff axle tube. Its the thing with two vacuum hoses and an electrical plug attached to it. You can either drain the diff fluid before you do this or it will spill out once its broken loose. I did the latter because I just changed the diff fluids and didnt want to waste much. By doing it this way you save about 1/4 - 1/3 of whats in the diff.
2: Once the ADD modulator is off, its probably best to replace it with a working one, or to eliminate ADD, slide the shaft inside the axle tube into the "4wd" position so the gears are connected. Slide the fork on the ADD modulator to the 4wd side and cap off the vacuum hoses.
3: Put back together. Make sure the sleeve and fork stay in the 4wd position before you button it all back up. I practiced putting it back in without accidently moving the fork and sleeve before I applied FIPG and put it back together. Once you are able to get it back on without moving the sleeve and fork, put silicone gasket maker (FIPG) on the diff to seal the modulator back up. Fill her up with diff fluid once its all back together and check for leaks. andd make sure the 4wd engages now
If you went with blocking off the ADD, you will probably need manual hubs so the front drive-train isnt spinning and bind up. You should be able to find a used modulator at a junk yard or be able to repair the old one. How? I dont know. I just plugged mine up because I had manual hubs already. Hope this helps. good luck.
1. Unbolt the ADD modulator on the front of the front diff axle tube. Its the thing with two vacuum hoses and an electrical plug attached to it. You can either drain the diff fluid before you do this or it will spill out once its broken loose. I did the latter because I just changed the diff fluids and didnt want to waste much. By doing it this way you save about 1/4 - 1/3 of whats in the diff.
2: Once the ADD modulator is off, its probably best to replace it with a working one, or to eliminate ADD, slide the shaft inside the axle tube into the "4wd" position so the gears are connected. Slide the fork on the ADD modulator to the 4wd side and cap off the vacuum hoses.
3: Put back together. Make sure the sleeve and fork stay in the 4wd position before you button it all back up. I practiced putting it back in without accidently moving the fork and sleeve before I applied FIPG and put it back together. Once you are able to get it back on without moving the sleeve and fork, put silicone gasket maker (FIPG) on the diff to seal the modulator back up. Fill her up with diff fluid once its all back together and check for leaks. andd make sure the 4wd engages now
If you went with blocking off the ADD, you will probably need manual hubs so the front drive-train isnt spinning and bind up. You should be able to find a used modulator at a junk yard or be able to repair the old one. How? I dont know. I just plugged mine up because I had manual hubs already. Hope this helps. good luck.
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