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Old 01-14-2003, 10:02 PM
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Post narrowing a 12 bolt

I want to narrow my owne rear end for me 1980 350cbi chevette. I am a 10yr machinist with allthe equiptment I need and a strong mechanic back ground. I need to know specifics how to. Can anyone help.

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Old 01-15-2003, 07:02 PM's Avatar
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the 12-bolt does not narrow well, not enuf meat in the axles where you have to cut the new spline. use a 9" ford the axle is thicker and you can turn down the od. then use a index head and cunvolute cutter to cut the splines, this stuff is TUFF and hard to machine. you have to build a jig to narrow the housings, i used a piece of bar the same size as the id of the axle bearings, about 5 ft long, then machined round spacers for the center section (to simulate axle in bearings) after the jig is made you can cut the housing to any width, then just weld the ends back on, just keep everything square and turning free while you are welding.
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Old 01-15-2003, 07:15 PM
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The axles in a 12 bolt cant be narrowed, they must be replaced because they have a tapered shaft. also a ford 9in is hard to come by and they are to expensive when, and if you do find one. I was wanting to know details on narrowing a 12 bolt housing. ie tricks, what to watch for, things like that.
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Old 01-16-2003, 07:08 AM
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Bob's advice is pretty straight-forward for narrowing any rear end housing. Make yourself a jig as he described. Machine some spacers to take the place of the carrier bearings and the axle bearings, with a machined bar going through all four of these spacers. Make sure that the bar turns freely as you weld the ends back on the housing, measure everything carefully and order aftermarket axles to fit.
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