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Post by spud on Feb 8, 2020 17:25:59 GMT -8
I have noticed that... the early javelin has two rear end widths. And rear ends have two distinct housing widths, one housing is about 52.5 inches wide ( narrower of the two) and the wider one is 53” wide. I have assumed that the wider housing came out later, however i do not know this for fact. I recently removed a narrow 3.15 open diff from a 70 javelin and today i bought a wider 3.15 open from another 70 javelin. I also have a narrow 3.91 power lock from a 68 amx. ( the power lock is not a “ twin grip” its a different type of posi) . I have two “wide”2.87 open axle assemblies that came from 69 javelins. I have a 71 hornet rear, a 2.87 open and its narrow, and another hornet rear that is wide... Does anyone actually know any facts on this phenomenon? I do not see any correlation to year or ratio or differential type relative to what width axle assembly i might find?
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Post by sc397 on Feb 8, 2020 18:14:17 GMT -8
I thought that the 1968 and 1969 was the same but they changed in 1970.
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Post by spud on Feb 9, 2020 1:17:06 GMT -8
I had a 70 amx. The rear from that car was a narrow 3.15 twin grip. I currently have a 70 360 auto go pack ram air car. It has a narrow 3.15 open. I believe both of these cars had the original rear. I bought a wide 3.15 open from a 70 ram air javelin today. Once again i think it was probably the original rear. So i dont see any pattern to this at all. I dunno if a half inch matters much to most but when you are trying to fit bigger tires it makes a big difference. Its only a quarter inch per side. Still its just another odd thing to ponder on. Or keep your eye out for. I know most people arent intetested in keeping a selection of rear axle assemblies on hand like me but they are important to me, and a great tuning asset. I have 5 different ford 9 “ center sections , and probably should just get a proper ford housing for this car too. But the amc 20 is lighter and more efficient using less power, and that counts big for weak 304 fun.
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Post by PHAT69AMX on Feb 11, 2020 15:35:57 GMT -8
Here is some bullshit I typed up a long time ago using the Track Width Dimensions published in the AMA / SAE Papers: ( but ya never know if any typo errors were made or not, but do my best to avoid them )
6" rim measures 7 inches wide / 2 = 3.5 b.s. when there is 0.0 Offset so stock 6" rims with 4" backspace have 1/2" Offset so Hub to Hub is greater than Track Width by 2 times 1/2 offset, or 1 inch
Hub to Hub, both front and rear, is 1.0 inch greater than stock Track Width dimensions based on stock wheel offset. -BUT- ? what about front 4-piston disc brake spacers ?
1968-69 Dims from AMA Data sheets: 59.38 inch = Front Hub to Hub = 58.38 Stock Front Track + 1.0 inch 58.00 inch = Rear Hub to Hub = 57.00 Stock Rear Track + 1.0 inch
1970 dims from AMA Data sheets: 60.30 inch = Front Hub to Hub = I6 59.30 Stock Front Track + 1.0 inch 60.70 inch = Front Hub to Hub = V8 59.70 Stock Front Track + 1.0 inch 58.00 inch = Rear Hub to Hub = 57.00 Stock Rear Track + 1.0 inch
This is from the 1967-1972 AMC Parts Manual and may provide some clues ?
well.... it says this forum has exceeded it's file space limits.... I tried...
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Post by sc397 on Feb 12, 2020 7:15:14 GMT -8
I blame it all on the Rebel Machine wheels... I always thought that the pig was offset differently for 1970 but what do I know.
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Post by spud on Feb 12, 2020 8:56:25 GMT -8
I love ya phat but once again it all cooks dow to a measurement of the axle assembly. On an assembled rear axle I just measure across the wheel mounting surface of the drums with a tape measure. Try it on a few rearends and it wont take long before you see what im talking about. And in my quest i am finding more narrow ones in 70 cars...i realize 50 years after the fact a lot of rear axle swaps have been done . I mark the wide housings with a “w” and narrow ones with an “n” to tell them apart. Measure yours and see what you get. It wont take long till you see why moser cant just send you axles... if you have a bare housing a narrow one will be 52 1/4 and a wide one is 52 3/4... and dont assume anything, you could have either one.
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