Hey, I am not knowledgeable about this stuff, can anyone i.d. my differential? It is a 10-bolt the bolts are not seen looking at the pumpkin from the rear of the car (they are on the front side of the case) and it has these numbers stamped on it J 186 and 3725899 GM It does not have a P stamped on it but there is a big O or zero. Also we think it acts like a posi, when we spin one rear wheel the opposite wheel turns backward. I bought the car as a shell with no interior or drivetrain, we're messing around underneath this week trying to install the fuel tank and bend up a 3/8" fuel line and get a little undercoating into the wheel wells and rocker areas at least.
What is my rear end?
garlok
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Hey, I am not knowledgeable about this stuff, can anyone i.d. my differential? It is a 10-bolt the bolts are not seen looking at the pumpkin from the rear of the car (they are on the front side of the case) and it has these numbers stamped on it J 186 and 3725899 GM It does not have a P stamped on it but there is a big O or zero. Also we think it acts like a posi, when we spin one rear wheel the opposite wheel turns backward. I bought the car as a shell with no interior or drivetrain, we're messing around underneath this week trying to install the fuel tank and bend up a 3/8" fuel line and get a little undercoating into the wheel wells and rocker areas at least.
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117 Posts
Sounds like a stock 10 bolt. I don't think it is a posi though. If it were I believe that while turning one wheel the other would want to turn the same direction. I don't know what the O means. Maybe a production plant like Oakland??? Maybe it is just a casting mark. Mine has a mark just before the A317 (my diff #) that might be mistaken for an O but I think it is just a casting mark. Mine has a BIG GM on it. Does yours have a steel tag on one of the nuts? I posted a question about the id tag not long ago and got this answer.
Rog
Then got this:Just to save time.
![Image]()
Hope this helps you out.According to the comment's posted in the thread about a week ago the book show 336 and 355 are incorrect a 336 has one hole and a 355 has two?Randall
Rog
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12,101 Posts
That means it is NOT a posi, if it turns easily. If it was a posi, the wheels would turn in the same direction due to the clutches in the posi.
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244 Posts
Well, my memory was wrong...today we got the car up and did the spin-one- wheel test and lo and behold...they both turn the same way. So it seems it IS a posi...cool. Tried to count the revs of driveshaft per one wheel revolution and it is a bit less than three and a half, so I'm guessing it's a 3.36 which is fine with me, as we dropped a pretty mild 350 and a 700R4 in it. Got a Corvette converter which is supposed to be about an 1800 stall. We installed the new driveshaft today, and the major task now is to bend up a new fuel line...the one in there is 5/16 and I want a 3/8 but the shipping cost for a preformed one is mucho bucks. I haven't bent tubing since airplane mechanic school in the early 70's. I'm hoping I can use my stock 5/16 line for a pattern and just install a new 3/8 line on the same inside the frame routing. This is not a show car but a nice driver. Anybody got tips on bending steel tubing? I think I'm going to look for ridgid products for bending and flaring.
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