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1978 280z
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Discussion Starter #1
So my 280z rear diff is pretty much toast. I'm looking at a 240z diff to replace it. Does the 240z diff fit the 280z? (Is it bolt on) If not, how difficult would it be to make it fit. Thanks.
 

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They all fit each other except for the very early series 1 differential which i think has flanges that point diagonally instead of laterally.
 

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Also need to be sure you have an r180 or r200 to get an exact replacement. Then you will have to get the right pieces to fit if they are not the same size. Then you have gear ratios. See here:
 

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1978 280z
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Discussion Starter #4
Also need to be sure you have an r180 or r200 to get an exact replacement. Then you will have to get the right pieces to fit if they are not the same size. Then you have gear ratios. See here:
So is there an identifying number stamped into the casing or anything?. If not how do you know the difference? The fella I'm buying from said it was removed from a 240z. He doesn't know much else.
 

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I'm not sure if its stamped on there but its most likely a 180 - the 160s came on the VERY early cars. An easy way to tell if its a 180 or 200 is just the shape of the diff when looking at it from the rear of the car - the r180 back plate is rectangular, the r200's black plate is more circular.
 

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Use the chart I posted with your year of production and transmission your car came with. Slight chance you have an R180, most 280z had an r200.
 

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Use the chart I posted with your year of production and transmission your car came with. Slight chance you have an R180, most 280z had an r200.
Manual 280 got the r200, auto trans 280s got the r180
 

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That list is accurate but it's best to double check what you have. The diff could have been changed out by someone previous so it's best to double check what you have to make sure. There aren't any numbers on the outside of the differential to help you. Measure the distance across on the diff rear cover to identify what you have. The R180 is 6.5 inches across and the R200 is 8.5 inches across. Nothing is interchangeable between the diffs. For the R200 there is a variable in the front flanges, go by the bolt hole size in the flange. They are either 8mm or 10mm. The 75 uses a 10mm and all the other years from 74-80 all use the 8mm bolts. Pay no attention to the shape of the front flange, just the bolt size. All R180 front flanges only use the 8mm bolt size. The driveshaft flange depends on the bolt hole size as well. The rear support strap or mustache bar will only fit the diff size (or model) it was designed for. To change the diff model you'd have to change at least the mustache bar. Z man of Washington
 
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