Semi Float Rear Diff Question (1 Viewer)

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Sep 8, 2009
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MA
In doing a rear disc brake conversion, like a moron, I loosened the carrier bolts holding the rear diff in place. Thought I had to in order to get at the c clips and remove the semi floating axles. I removed the rear drums and reinstalled the axles. I put everything back together (after the spider gear came apart) and bolted it up. Unfortunately, the diff won’t spin. When I loosen the carrier bolts holding the diff in place, specifically on the ring gear side, it spins. Clearly. I’ve f’d something up.

My questions is...do I have to remove the diff in order to a properly align the carriers, bearings and diff adjusting nuts or can I do this while it’s in place on the truck?
 
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Damn. That’s what I thought. Was hoping for a trick of some sort. Thanks for the help.
 

65swb45

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IMO, if it’s been behind the V8 for any length of time, it’s not worth the effort of re-setting. Good used low mileage 3rds are just too readily available to put $$ into one that’s been run behind a V8.
 
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Good advice all around. Thank you.
What are some vendor options for a third member? Maybe it would be a good time to consider a locking rear as well.
 

pb4ugo

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I think, if your rearend worked properly and smoothly b4 and the pinion has no play, there's no real difference between resetting the backlash and buying a good used 3rd member with unknown miles. If all the internals look good, resetting the backlash is not that difficult and doesn't require tearing the whole 3rd apart. The hardest part is getting the 3rd out of the rearend housing.

You can add a lunchbox locker, like a lockrite, powertrax, or aussie by removing the spider gears and replace them with the lunchbox. If you go to a selectable locker like an ARB, or non selectable locker like a Detroit locker, then it requires more work. They require replacing the carrier, which is what your ring gear is bolted to. If I were going that direction, I would probably rebuild the whole dif with new ring & pinion, bearings and seals, which is alot more expensive and more labor intensive. The lunchbox lockers don't operate as smoothly and as quietly as the units that require replacing the whole carrier.
 
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And here's another remote possibility that could be causing your problem, without it being your third member; If you transferred a rear disc brake conversion kit from a semi floating rear end onto your full floater, or if you were sold a kit designed for a semi floating rear end, the rotor will be hung up on the axle housing, preventing you from spinning the third member. Your rotor center holes would be machine open to 4.174" diameter, but for full floating rear ends the inside diameter of the rotor must also be machined/opened up to 7.360" to clear the axle housing flanges.
 

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