Help Identify 8 1/4 differential?

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DesertRat

DesertRat

Leading edge boomer
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I have an 8 1/4 cone type shur grip complete rear end I bought on CL. The casting #'s on the case is #3723599, . I need to start buying parts for this unit and I want to make sure I am asking for the right stuff. In would like to buy a new back cover plate as the chrome aftermarket one does not fit with what I am building. Any help will be much appreciated!
TIA, Rat
 
I have been searching for the ID of this rear end for days. The seller claimed it is from a 1974 duster. The actual casting number on the differential housing is #3723599. I have the Motorbooks workshop Chrysler muscle car parts interchange manual for 68 to 74 but is does not list that casting number. Makes me think it may be a different year. In a post by martin7170 to this site in 2007, this is an exact fit for my a-body. Can anyone reccomend a way to verify the year of this unit?
TIA-Rat
 
This should clear it up.

axle.jpg
 
Oh ok. Cain't you measure it anf know? I mean an A body is what....like 43" center to center on the perches?
 
For what it's worth a build date of 9/73 A Body 8.25 has a casting number of 2852905
 
Badsport said:
So is the chart incorrect do you think? It shows that number a B as well.
Click to expand...


The 8.25 I have is definitely for an A Body based on the perch and housing width. It looks like its all original. I see that chart doesn't even list an A Body 8.25; that 905 number looks like a part number and could be a carry-over from the 69/70 B for the A's. I do know that it takes the early bearings, races, etc. Maybe someone else who has a 73/76 A 8.25 can check and see what their numbers are.
 
Well, it looks like badsport dialed it in. I believe this has the correct spring perch dimensions for my car but the overall width is about 1.75" narrower. I am questioning whether I should put it in the car now but at least I have a model to look for to buy parts if I decide to try it. Thanks everyone for your input, I really appreciate the help. May have to sell this one and look for an
8 3/4 as that seems to be the one of choice anyway. This one is supposed to be a 3:21 to 1 ratio which would be perfect for my build.
DR
 
The carrier bearing size changed at some point. I think i have an older one.
 
My 8 1/4 spring perches match the existing 7 1/4 dimensions at 43.02" so that part works fine. Per a chart off moparts that makes the setup a 73 to 76 A-body unit. Dont know why the casting numbers dont work but I am going to assume it is an anomoly at this point. The width on the 8 1/4 unit is 1.8" narrower per the chart which could move the back plates .9" closer to the leaf springs. I know the brake drums are wider so I am hoping that the axle face to face is the same as the 7 1/4 unit so my 15" LBP rallys will fit without rubbing. It looks like this unit will work on the surface, just need to buy new durms, shoes and cylinders for the 8 1/4 before installing.
DR
 
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